Real-World Treatment Patterns Among Patients with Type 2 Diabetes Mellitus Initiating Treatment with Oral Semaglutide.

INTRODUCTION: The treatment landscape for type 2 diabetes mellitus (T2DM) is complex and constantly evolving, and real-world evidence of prescribing patterns is limited. The objectives of this study were to characterize lines of therapy (LOTs), calculate the length of time spent on each LOT, and identify the reasons for the LOT end among patients who initiated oral semaglutide for T2DM. METHODS: This retrospective, claims-based study included commercial and Medicare Advantage adults with T2DM. Data from November 1, 2019, and June 30, 2020, were obtained from Optum Research Database. Patients with ≥ 1 claim for oral semaglutide and continuous health plan enrollment for ≥ 12 months prior to (baseline period) and ≥ 6 months following (follow-up period) the date of the first oral semaglutide claim were included. LOT 1 began on the date of the first oral semaglutide claim. The start date of any subsequent LOTs was the date of the first claim for an additional non-insulin anti-diabetic drug class or a reduction in drug class with use of commitment medications. The LOT ended at the first instance of medication class discontinuation, change in regimen or end of follow-up. RESULTS: Of the 1937 patients who initiated oral semaglutide, 950 (49.0%) remained on their initial regimen over the 6-month follow-up period, 844 (43.6%) had at least one subsequent LOT, and 89 (4.6%) had at least two subsequent LOTs. Among patients with more than one LOT, approximately 20%-25% used oral semaglutide as monotherapy or combination therapy during LOTs 2 and 3. Metformin was frequently used during treatment across all LOTs. CONCLUSION: This study provides insight for physicians and payers into the real-world prescribing practices within the first 6 months following oral semaglutide initiation and fills the gap in understanding the frequency of regimen changes in the constantly evolving and complex environment of T2DM care.

Type 2 diabetes mellitus is a disease which, over time, can cause higher than normal levels of sugar in the blood (hyperglycemia) which can be harmful if not treated. Treatment for type 2 diabetes mellitus can be complex, and how doctors prescribe medications is always changing. For some people with type 2 diabetes mellitus who are overweight or obese, it is recommended for patients to use certain medications that can help with weight management such as semaglutide and metformin. This study aims to fill gaps in current treatment knowledge about type 2 diabetes mellitus patients and their treatment of oral semaglutide. Researchers in this study explored how patients treated with oral semaglutide differentiated among line of therapies, how long patients stuck to them and why they stopped. The study found that those patients who started with oral semaglutide, almost half of those patients stuck to their initial treatment plan for the entire 6 months. When it came to the top ten treatment plans, about 20% of patients used oral semaglutide alone and about 25% of patients used oral semaglutide plus an additional treatment option. Metformin was frequently used during treatment across all line of therapies. There is little information on the real-life setting of treatment after the start of therapy for type 2 diabetes mellitus. The results from this study show what happens when patients start using oral semaglutide and helps healthcare providers understand how often treatment plans can change in type 2 diabetes mellitus care.

Real-world glycated haemoglobin changes among type 2 diabetes mellitus patients treated with a maintenance dose of 7 mg or 14 mg of oral semaglutide.

AIM: To describe the change in glycated haemoglobin (HbA1c) among patients with type 2 diabetes following treatment with a 7 or 14 mg maintenance dose of oral semaglutide. MATERIALS AND METHODS: This retrospective, claims-based study included adult patients with type 2 diabetes with a pre-index HbA1c of ≥7%, initiating treatment with oral semaglutide between 1 November 2019 and 30 June 2020; the patients had continuous health plan enrolment for ≥12 months before (pre-index) and ≥6 months following (post-index) the date of the first oral semaglutide claim (index). Patients were required to have a maintenance dose of 7 or 14 mg. Pre-index demographic and clinical characteristics were captured, as were doses at initiation and prescriber specialty. The change in HbA1c between the latest post-index and pre-index HbA1c measurements was calculated among all patients and among those with ≥90 days of continuous treatment (persistent patients). RESULTS: This study included 520 patients, most of whom had a complex medical history, experienced a range of comorbidities and received an average of 11.5 different classes of medications during the pre-index period. The mean HbA1c reduction during the 6-month post-initiation period was 1.2% (p < .001) for all patients and 1.4% (p < .001) for persistent patients. CONCLUSIONS: In this real-world study, patients with a pre-index HbA1c ≥7% who initiated treatment with oral semaglutide with a 7 or 14 mg maintenance dose had significantly lower HbA1c levels following treatment.

Real-World Hemoglobin A1c Changes, Prescribing Provider Types, and Medication Dose Among Patients with Type 2 Diabetes Mellitus Initiating Treatment with Oral Semaglutide.

INTRODUCTION: Given the lack of real-world data on oral semaglutide use outside clinical trials, the purpose of this study was to describe dose, prescriber specialty, and change in hemoglobin A1c (HbA1c) after 6 months of oral semaglutide treatment for patients with type 2 diabetes mellitus (T2DM). METHODS: This was a retrospective study among adult patients with T2DM with ≥ 1 claim for oral semaglutide between November 1, 2019`1-June 30, 2020. Patients had continuous health plan enrollment ≥ 12 months prior to (pre-index) and ≥ 6 months following (post-index) the date of the first oral semaglutide claim (index). Dose at initiation and specialty of the prescribing provider were captured. Change in HbA1c between the last post- and pre-index HbA1c measurement was calculated. Patients were stratified by pre-index HbA1c ≥ 9% (poorly controlled) and HbA1c < 9%. RESULTS: A total of 744 HbA1c < 9% and 268 poorly controlled patients were included in the study. Most patients had an initial oral semaglutide dose of 7 mg (49.3%) or 3 mg (42.9%), prescribed most frequently by a primary care provider (27.8%). Mean HbA1c reduction was 0.8% (p < 0.001). Patients with poorly controlled T2DM had greater HbA1c reductions than patients with HbA1c < 9% (2.0% versus 0.4%, p < 0.001). Patients persistent with oral semaglutide (≥ 90 days continuous treatment) had a mean HbA1c reduction of 0.9% (p < 0.001); persistent patients with poorly controlled T2DM had a mean reduction of 2.5%. CONCLUSIONS: Patients with T2DM in this study experienced significant reductions in HbA1c within 6 months following initiation of oral semaglutide. Patients with a higher starting HbA1c experienced greater HbA1c reductions. The initial dose of oral semaglutide was higher than prescribing instructions indicated for more than half of the study patients.

Impact of chronic fibrosing interstitial lung disease on healthcare use: association between fvc decline and inpatient hospitalization.

BACKGROUND: Many types of interstitial lung diseases (ILDs) may transition to progressive chronic-fibrosing ILDs with rapid lung function decline and a negative survival prognosis. In real-world clinical settings, forced vital capacity (FVC) measures demonstrating progressive decline may be linked to negative outcomes, including increased risks of costly healthcare resource utilization (HRU). Thus, we assessed the relationship between rate of decline in lung function and an increase in HRU, specifically inpatient hospitalization, among patients with chronic fibrosing ILD. METHODS: This study utilized electronic health records from 01-Oct-2015 to 31-Oct-2019. Eligible patients (≥ 18 years old) had ≥ 2 fibrosing ILD diagnosis codes, clinical activity for ≥ 15 months, and ≥ 2 FVC tests occurring 6 months apart. Patients with missing demographic data, IPF, or use of nintedanib or pirfenidone were excluded. Two groups were defined by relative change in percent of predicted FVC (FVC% pred) from baseline to 6 months: significant decline (≥ 10%) vs. marginal decline/stable FVC (decrease < 10% or increase). The primary outcome was defined as the occurrence of an inpatient hospitalization 6 months after the first FVC value. Descriptive and multivariable analysis was conducted to examine the impact of FVC decline on occurrence of inpatient hospitalization. RESULTS: The sample included 566 patients: 13% (n = 75) with significant decline and 87% (n = 491) with marginal decline/stable FVC; their mean age (SD) was 65 (13.7) years and 56% were female. Autoimmune diagnoses were observed among 40% of patients with significant decline, and 27% with marginal decline/stable FVC. The significant decline group had better lung function at baseline than the marginal/stable group. For patients with FVC% <80% at baseline, reduction of FVC% ≥10% was associated with significantly increased odds of an inpatient hospitalization (odds ratio [OR] 2.85; confidence interval [CI] 1.17, 6.94 [p = 0.021]). CONCLUSION: Decline in FVC% ≥10% was associated with increased odds of inpatient hospitalization among patients with reduced lung function at baseline. These findings support the importance of preserving lung function among patients with fibrosing ILD.

Association between N-Terminal Pyrenes Stabilizes the Collagen Triple Helix.

Collagen model peptides featuring the fluorophore pyrene at their N-termini have been synthesized, and their thermal denaturation has been examined using circular dichroism (CD) and fluorescence spectroscopies. Flanking the (Pro-Hyp-Gly)7 core of the peptide monomers at positions 1 and/or 23 in the primary sequence, Lys residues were introduced to ensure water solubility. Triple helices derived from such peptides show a broad excimer emission at ∼480 nm, indicative of interaction between the pyrene units. CD experiments show that the fluorophores enhance helix stability primarily through entropic effects. Unfolding temperatures (Tm) increase by up to 7 °C for systems with N-terminal lysine residues and by up to 21 °C for systems in which the first-position Lys is replaced by Ala. Tm values derived from fluorescence measurements (at 50 µM) typically lie within ∼1 °C of those obtained using CD (at 200 µM). Computational modeling in a water continuum using B3LYP-GD3 and M06-2X functionals predicts that face-to-face association of fluorophores can occur while H-bonding within the [(POG)n]3 assembly is retained. Such parallel stacking is consistent with hydrophobically driven stabilization. Labeling collagen peptides with pyrene is a synthetically simple way to promote triple helicity while providing a means to obtain Tm data on relatively dilute samples.

Healthcare Resource Utilization, Cost and Clinical Outcomes in Patients Diagnosed with COPD Initiating Tiotropium Bromide/Olodaterol versus Fluticasone Furoate/Umeclidinium/Vilanterol Based on Exacerbation History.

Background: ATS and GOLD guidelines recommend treating low-exacerbation risk COPD patients with dual (LAMA/LABA) agents and reserving triple therapy (TT; LAMA/LABA and inhaled corticosteroids [ICS]) for severe cases with higher-exacerbation risk. However, TT often is prescribed across the COPD spectrum. This study compared COPD exacerbations, pneumonia diagnosis, healthcare resource utilization, and costs for patients initiating tiotropium bromide/olodaterol (TIO/OLO) and a TT, fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI), stratified by exacerbation history. Methods: COPD patients who initiated TIO/OLO or FF/UMEC/VI between 06/01/2015-11/30/2019 (index date=first pharmacy fill-date with ≥30 consecutive treatment days) were identified from the Optum Research Database. Patients were ≥40 years old and continuously enrolled for 12 months during the baseline period and ≥30 days during follow-up. Patients were stratified into GOLD A/B (0-1 baseline non-hospitalized exacerbation), No exacerbation (subset of GOLD A/B), and GOLD C/D (≥2 non-hospitalized and/or ≥1 hospitalized baseline exacerbation). Baseline characteristics were balanced with propensity score matching (1:1). Adjusted risks of exacerbation, pneumonia diagnosis, and COPD and/or pneumonia-related utilization and costs were evaluated. Results: Adjusted exacerbation risk was similar in GOLD A/B and No exacerbation subgroups, and lower in GOLD C/D for FF/UMEC/VI versus TIO/OLO initiators (hazard ratio: 0.87; 95% CI: 0.78, 0.98, p=0.020). Adjusted pneumonia risk was similar between cohorts across the GOLD subgroups. Adjusted COPD and/or pneumonia-related population annualized pharmacy costs were significantly higher for FF/UMEC/VI versus TIO/OLO initiators across subgroups, p<0.001. Adjusted COPD and/or pneumonia-related population annualized total healthcare costs were significantly higher for FF/UMEC/VI versus TIO/OLO initiators in the GOLD A/B and No exacerbation, subgroups, p<0.001 (cost ratio [95% CI]: 1.25 [1.13, 1.38] and 1.21 [1.09, 1.36], respectively), but similar in the GOLD C/D subgroup. Conclusion: These real-world results support ATS and GOLD recommendations for treating low-exacerbation risk COPD patients with dual bronchodilators and TT for more severe, higher-exacerbation risk COPD patients.

Clinical and economic outcomes in patients with chronic obstructive pulmonary disease initiating maintenance therapy with tiotropium bromide/olodaterol or fluticasone furoate/umeclidinium/vilanterol.

BACKGROUND: Clinical practice guidelines recommend dual long-acting muscarinic antagonists (LAMAs)/long-acting ß2agonists (LABAs) as maintenance therapy in patients with chronic obstructive pulmonary disease (COPD) and dyspnea or exercise intolerance. Escalation to triple therapy (TT) (LAMA/LABA/inhaled corticosteroid) is conditionally recommended for patients with continued exacerbations on dual LAMA/LABA therapy. Despite this guidance, TT use is widespread across COPD severities, which could impact clinical and economic outcomes. OBJECTIVE: To compare COPD exacerbations, pneumonia events, and disease-related and all-cause health care resource utilization and costs (in 2020 US dollars) in patients initiating fixed-dose combinations of either LAMA/LABA (tiotropium/olodaterol [TIO + OLO]) or TT (fluticasone furoate/umeclidinium/vilanterol [FF + UMEC + VI]). METHODS: This retrospective observational study of administrative claims included patients with COPD aged 40 years or older initiating TIO + OLO or FF + UMEC + VI from June 2015 to November 2019. TIO + OLO and FF + UMEC + VI cohorts in the overall and maintenance-naive populations were 1:1 propensity score matched on baseline demographics, comorbidities, COPD medications, health care resource utilization, and costs. Multivariable regression compared clinical and economic outcomes up to 12 months in FF + UMEC + VI vs TIO + OLO postmatched cohorts. RESULTS: After matching, there were 5,658 and 3,025 pairs in the overall and maintenance-naive populations, respectively. In the overall population, the risk of any (moderate or severe) exacerbation was 7% lower in FF + UMEC + VI vs TIO + OLO initiators (adjusted hazard ratio [aHR] = 0.93; 95% CI = 0.86-1.0; P = 0.047). There was no difference in the adjusted risk of any exacerbation in the maintenance-naive population (aHR = 0.99; 95% CI = 0.88-1.10). Pneumonia risk was not statistically different between cohorts in the overall (aHR = 1.12; 95% CI = 0.98-1.27) and maintenance-naive (aHR = 1.13; 95% CI = 0.95-1.36) populations. COPD- and/or pneumonia-related adjusted total annualized costs (95% CI) were significantly greater for FF + UMEC + VI vs TIO + OLO in the overall ($17,633 [16,661-18,604] vs $14,558 [13,709-15,407]; P < 0.001; differences [% of relative increase] = $3,075 [21.1%]) and maintenancenaive ($19,032 [17,466-20,598] vs $15,004 [13,786-16,223]; P < 0.001; $4,028 [26.8%]) populations, with significantly higher pharmacy costs with FF + UMEC + VI (overall: $6,567 [6,503-6,632] vs $4,729 [4,676-4,783]; P < 0.001; $1,838 [38.9%]; maintenance-naive: $6,642 [6,560-6,724] vs $4,750 [4,676-4,825]; P < 0.001; $1,892 [39.8%]). CONCLUSIONS: A lower risk of exacerbation was observed with FF + UMEC + VI vs TIO + OLO in the overall population but not among the maintenance-naive population. Patients with COPD initiating TIO + OLO had lower annualized costs than FF + UMEC + VI initiators in the overall and maintenance-naive populations. Thus, in the maintenance-naive population, initiation with dual LAMA/LABA therapy per practice guidelines can improve real-world economic outcomes. Study registration number: ClinicalTrials.gov (identifier: NCT05127304). DISCLOSURES: The study was funded by Boehringer Ingelheim Pharmaceuticals, Inc (BIPI). To ensure independent interpretation of clinical study results and enable authors to fulfill their role and obligations under the ICMJE criteria, BIPI grants all external authors access to relevant clinical study data. In adherence with the BIPI Policy on Transparency and Publication of Clinical Study Data, scientific and medical researchers can request access to clinical study data after publication of the primary manuscript in a peer-reviewed journal, regulatory activities are complete and other criteria are met. Dr Sethi has received honoraria/fees for consulting/speaking from Astra-Zeneca, BIPI, and GlaxoSmithKline. He has received consulting fees for serving on data safety monitoring boards from Nuvaira and Pulmotect. He has received consulting fees from Apellis and Aerogen. His institution has received research funds for his participation in clinical trials from Regeneron and AstraZeneca. Ms Palli was an employee of BIPI at the time the study was conducted. Drs Clark and Shaikh are employees of BIPI. Ms Buysman and Mr Sargent are employees and Dr Bengtson was an employee of Optum, which was contracted by BIPI to conduct this study. Dr Ferguson reports grants and personal fees from Boehringer Ingelheim during the conduct of the study; grants from Novartis, Altavant, and Knopp; grants and personal fees from AstraZeneca, Verona, Theravance, Teva, and GlaxoSmithKline; and personal fees from Galderma, Orpheris, Dev.Pro, Syneos, and Ionis outside the submitted work. He was a paid consultant for BIPI for this study. The authors received no direct compensation related to the development of the manuscript. BIPI was given the opportunity to review the manuscript for medical and scientific accuracy as well as intellectual property considerations.

Synthesis of redox-active fluorinated 5-hydroxytryptophans as molecular reporters for biological electron transfer.

Fluorinated 5-hydroxytryptophans (Fn-5HOWs) were synthesized in gram scale quantities and incorporated into a ß-hairpin peptide and the protein azurin. The redox-active Fn-5HOWs exhibit unique radical spectroscopic signatures that expand the function of as probes for biological electron transfer.

Side-Chain Protonation States of a Fluorescent Arginine.

An arginine derivative with a fluorescent side-chain, Boc-Arg(Nap)-OH, was prepared by palladium(0)-catalyzed coupling of Boc-Arg-OH with a 4-bromonaphthalimide. The presence of the fluorophore lowers the pKa of the side-chain guanidinium group by several orders of magnitude, to 9.0 (±0.1), allowing the derivative to access an electrically neutral protonation state that is not generally available to arginine itself. Computational modeling (DFT) predicts that protonation takes place at the side-chain C═N atom that bears the fluorophore. Calculated electronic absorptions for the protonated (356 nm) and neutral species (440 nm) are in good agreement with experiment. When irradiated with light, excited-state proton transfer (ESPT) occurs from cationic side-chains to suitably basic solvents, resulting in fluorescence emission from the neutral species. Arg(Nap) can be incorporated into peptides with sterically accessible N-termini using specially adapted conditions of solid-phase peptide synthesis.

Decarboxylative and dehydrative coupling of dienoic acids and pentadienyl alcohols to form 1,3,6,8-tetraenes.

Dienoic acids and pentadienyl alcohols are coupled in a decarboxylative and dehydrative manner at ambient temperature using Pd(0) catalysis to generate 1,3,6,8-tetraenes. Contrary to related decarboxylative coupling reactions, an anion-stabilizing group is not required adjacent to the carboxyl group. Of mechanistic importance, it appears that both the diene of the acid and the diene of the alcohol are required for this reaction. To further understand this reaction, substitutions at every unique position of both coupling partners was examined and two potential mechanisms are presented.

Incorporation of fluorophore-cholesterol conjugates into liposomal and mycobacterial membranes.

Fluorescently-labeled steroids that emit intense blue light in nonpolar solvent (λem (CH2Cl2)≈440nm, ΦF=0.70) were prepared by treating cholesteryl chloroformate with 4-amino-1,8-naphthalimides. The lipid portion of the conjugates embeds into liposomal membrane bilayers in minutes, leaving the fluorophore exposed to the external aqueous environment. This causes a 40-nm red-shift in λem and significant quenching. DFT optimizations predict the conjugates to be about 30Å long when fully extended, but rotation about the linker group can bring the compounds into an 'L'-shape. Such a conformation would allow the cholesteryl anchor to remain parallel to the acyl chains of a membrane while the fluorescent group resides in the interfacial region, instead of extending beyond it. When incubated with Mycobacterium smegmatis mc2 155, a bacterial species known to use natural cholesterol, the labeled steroids support growth and can be found localized in the membrane fraction of the cells using HPLC. These findings demonstrate stable integration of fluorescent cholesterols into bacterial membranes in vivo, indicating that these compounds may be useful for evaluating cholesterol uptake in prokaryotic organisms.

Dimerization and anion binding of a fluorescent phospholipid analogue.

A diarylacetylene fluorophore featuring spatially separated urea and phosphocholine (PC) groups forms a macrocyclic "head-to-tail" dimer stabilized by NH(urea)···OP(PC) hydrogen bonds. At concentrations above ~2 × 10(-5) M in CH(2)Cl(2), the emission intensity of the dimer is quenched by HCO(3)(-) and H(2)PO(4)(-) but not by Cl(-) and NO(3)(-). Under more dilute conditions, all four anions are bound unselectively with association constants on the order of 10(5) M(-1).

Reframing caring as discursive practice: a critical review of conceptual analyses of caring in nursing.

This study critically examines the way in which the concept of caring is presented in the nursing literature through conceptual analytic approaches. A critical reflection on the potential consequences of representing a concept of caring as vague and ambiguous, yet central to ontology and epistemology in professional nursing is presented drawing on comparisons between the conceptual analyses of caring, and of structuralist perspectives of language, and how this potentially limits scholarship in this area. A search of the literature revealed nine conceptual papers. These papers highlight the self-referential characteristics of the concept of caring, and of analytical methods in general. It is proposed that this is the result of a systematic adherence to a rigid, structuralist view of language, whereby stable relationships between words and their meanings are assumed. An alternative perspective is offered by viewing caring as a discursive practice rather than a fixed conceptual entity, calling into question the role that the concept plays in nursing practice. A poststructuralist perspective requires caring to be perceived as a discourse of nursing that is fluid and contingent, rather than a central and guiding concept, opening up a new orientation for nursing scholarship in caring research.

Binding of carboxylic acids by fluorescent pyridyl ureas.

Fluorescent pyrid-2-yl ureas were prepared by treating halogenated 2-aminopyridines with hexyl isocyanate, followed by Sonogashira coupling with arylacetylenes. The sensors emit light of ∼360 nm with quantum yields of 0.05-0.1 in acetonitrile solution. Addition of strong organic acids (pK(a) < 13 in CH(3)CN) shifts the fluorescence band to lower energy, and clean isoemissive behavior is observed. Fluorescence response curves (i.e., F/F(0) vs [acid](total)) are hyperbolic in shape for CCl(3)COOH and CF(3)COOH, with association constants on the order of 10(3) M(-1) for both acids. (1)H NMR titrations and DFT analyses indicate that trihaloacetic acids bind in ionized form to the receptors. Pyridine protonation disrupts an intramolecular H-bond, thereby unfolding an array of ureido NH donors for recognition of the corresponding carboxylates. Methanesulfonic acid protonates the sensors, but no evidence for conjugate base binding at the urea moiety is found by NMR. An isosteric control compound that lacks an integrated pyridine does not undergo significant fluorescence changes upon acidification.

"Wurster-type" ureas as redox-active receptors for anions.

Four redox-active receptors, 1-4, based on the incorporation of p-phenylenediamine(s) within a urea framework, were synthesized, and the affinities of two for a series of anions were quantified through UV-vis and NMR spectroscopic studies. The structure of 1 was confirmed by X-ray crystallography. For the oxoanions studied, complex stabilities approached 10(6) M(-1) in acetonitrile and decreased with the decreasing basicity of the anion (CH(3)COO(-) > C(6)H(5)COO(-) > H(2)PO(4)(-) > NO(2)(-) > NO(3)(-)). The presence of the urea functionality caused an increase in the oxidation potential of the p-phenylenediamine subunit compared to that of free p-phenylenediamine. Electrochemical studies of the anion complexes revealed two-wave behavior with the appearance of a second oxidation wave cathodic to that in the free receptors and characteristic of the bound anion. Ab initio DFT studies of a representative acetate complex revealed the consequences of host oxidation state on complex structure.

Fluorous effects in amide-based receptors for anions.

Hybrid receptors designed to recognize both the sulfonate headgroup and the fluorous tail of perfluorooctanesulfonate (CF(3)(CF(2))(7)SO(3)(-), "PFOS") were prepared by coupling fluorinated carboxylic acids onto poly(aminomethyl)benzene scaffolds. Binding to PFOS, CF(3)SO(3)(-), p-TsO(-), and Cl(-) was monitored by (1)H NMR and isothermal titration calorimetry (ITC). In chloroform solvent, hydrogen-bonding to anions is accompanied by downfield shifts in the amide NH protons of the fluorinated receptors and by evolution of heat. Association constants for 1:1 complexation (K(assoc)) are >1000 M(-1). An analogous hydrocarbon receptor binds weakly to anionic guests (K(assoc) < 50 M(-1)). Ab initio calculations indicate that the differences in 1:1 binding strengths between fluorous and nonfluorous hosts cannot be ascribed to differences in NH donor acidities.

Hydrogen bonding vs steric gearing in a hexasubstituted benzene.

Treatment of hexakis(bromomethyl)benzene with excess NaN 3, followed by hydrogenation of the resultant polyazide, affords hexamine 3 in high yield. Coupling to six equivalents of nonanoic acid provides hexamide 5 without chromatographic purification. The NH resonance of 5 appears far downfield (approximately 9.7 ppm) in CDCl3 and is unaffected by changes in concentration or by addition of chloride or trifluoromethanesulfonate ions. DFT calculations predict that 5 exists as a bowl, with all six substituents intramolecularly H-bonded together on one side of the plane defined by the anchoring arene.

Wurster's crowns: a comparative study of ortho- and para-phenylenediamine-containing macrocyclic receptors.

Two series of isomeric, redox-responsive azacrown ethers based on ortho- and para-phenylenediamine (Wurster's crowns) have been synthesized and their properties explored through 13C NMR spectroscopy, electrospray ionization mass spectrometry, cyclic voltammetry, and X-ray crystallography. These crowns display strong affinity for alkali metal cations while maintaining comparable selectivity profiles to the parent crown ethers from which they are derived. Like Wurster's reagent (N,N,N',N'-tetramethyl-p-phenylenediamine or para-TMPD), the para-Wurster's crowns undergo two reversible one-electron oxidations. The integrity of the alkali metal ion complexes is maintained in the neutral and singly oxidized ligand states but not after removal of two electrons. In contrast, the oxidation of ortho-Wurster's crowns is scan rate dependent, occurring at potentials substantially higher than their para counterparts, with their complexes oxidizing irreversibly. X-ray crystal structures of representative complexes show, in all cases, participation of the redox-active phenylenediamine subunits in complex formation via direct bonding to the guest cation.

A theoretical investigation on the Wurster's crown analogue of 18-crown-6.

An ab initio, quantum mechanical study of the Wurster's crown analogue of 18-crown-6 and its interactions with the alkali metal cations are presented. This study explores methods for accurately treating large, electron-rich species while providing an understanding of the molecular behavior of a representative member of this class of crowns. The molecular geometries, binding energies, and binding enthalpies are evaluated with methods similar to those reported for the analysis of 18-crown-6 and its alkali metal complexes to facilitate direct comparison. Hybrid density functional methods are applied to gauge the effects of electron correlation on the geometries of the electron-rich phenylenediamine moiety present in the Wurster's crowns. While the structure of the crown ether backbone is largely unperturbed by the incorporation of the redox active functionality, the alkali metal binding enthalpies are uniformly stronger for the Wurster's crown complexes, adding 1.8 to 5.1 kcal/mol to the strength of the interaction, depending on cation type. The additional strength, due to the exchange of an oxygen donor atom in the crown ether backbone by a nitrogen donor supplied by the redox group, is tightly coupled to the rotation of the dimethylaminophenyl group with respect to the plane of the macrocycle. Gas-phase selectivities favor the more highly charge-dense cations, while the explicit addition of only a few waters of hydration in the calculations recovers the selectivities expected in solution. The alkali metal binding affinity to the singly oxidized Wurster's crown is significantly diminished, while it is completely eliminated for the doubly oxidized ligand.