Investigation of functionalized α-chloroalkyllithiums for a stereospecific reagent-controlled homologation approach to the analgesic alkaloid (-)-epibatidine.

Four putative functionalized α-chloroakyllithiums RCH2CHLiCl, where R=CHCH2(18 a), CCH (18 b), CH2OBn (18 c), and CH[O(CH2)2O] (18 d), were generated in situ by sulfoxide-lithium exchange from α-chlorosulfoxides, and investigated for the stereospecific reagent-controlled homologation (StReCH) of phenethyl and 2-chloropyrid-5-yl (17) pinacol boronic esters. Deuterium labeling experiments revealed that α-chloroalkyllithiums are quenched by proton transfer from their α-chlorosulfoxide precursors and it was established that this effect compromises the yield of StReCH reactions. Use of α-deuterated α-chlorosulfoxides was discovered to ameliorate the problem by retarding the rate of acid-base chemistry between the carbenoid and its precursor. Carbenoids 18 a and 18 b showed poor StReCH efficacy, particularly the propargyl group bearing carbenoid 18 b, the instability of which was attributed to a facile 1,2-hydride shift. By contrast, 18 d, a carbenoid that benefits from a stabilizing interaction between O and Li atoms gave good StReCH yields. Boronate 17 was chain extended by carbenoids 18 a, 18 b, and 18 d in 16, 0, and 68% yield, respectively; α-deuterated isotopomers D-18 a and D-18 d gave yields of 33 and 79% for the same reaction. Double StReCH of 17 was pursued to target contiguous stereodiads appropriate for the total synthesis of (-)-epibatidine (15). One-pot double StReCH of boronate 17 by two exposures to (S)-D-18 a (≤66 % ee), followed by work-up with KOOH, gave the expected stereodiad product in 16% yield (d.r.~67:33). The comparable reaction using two exposures to (S)-D-18 d (≤90% ee) delivered the expected bisacetal containing stereodiad (R,R)-DD-48 in 40% yield (≥98% ee, d.r.=85:15). Double StReCH of 17 using (S)-D-18 d (≤90% ee) followed by (R)-D-18 d (≤90% ee) likewise gave (R,S)-DD-48 in 49% yield (≥97% ee, d.r.=79:21). (R,S)-DD-48 was converted to a dideuterated isotopomer of a synthetic intermediate in Corey's synthesis of 15.

Iterative stereospecific reagent-controlled homologation using a functionalized α-chloroalkyllithium: synthesis of cyclic targets related to epibatidine.

Enantioenriched 1-chloro-2-(1,3-dioxolan-2-yl)ethyllithium was generated by PhLi initiated sulfoxide-ligand exchange and deployed in situ for sequential double stereospecific reagent-controlled homologation (StReCH) of B-(2-chloro-pyrid-5-yl) pinacol boronate. This process afforded highly functionalized contiguous stereodiad motifs (typically, % ee ≥ 98%, dr ≥ 85:15) amenable to subsequent annulative transformations as demonstrated by the concise synthesis (5-7 steps) of cyclic adducts related to the analgesic alkaloid epibatidine.

Dexlansoprazole: A proton pump inhibitor with a dual delayed-release system.

BACKGROUND: Dexlansoprazole, the dextrorotatory enantiomer of lansoprazole, is a proton pump inhibitor (PPI) formulated to have dual delayed-release properties. It is indicated for healing all grades of esophagitis, maintaining the healing of erosive esophagitis (EE), and treating heartburn associated with nonerosive gastroesophageal reflux disease. OBJECTIVE: This article reviews the pharmacology, pharmacokinetics, and pharmacodynamics of dexlansoprazole, as well as its clinical efficacy and tolerability. METHODS: MEDLINE (1966-April 2010) and International Pharmaceutical Abstracts (1970-April 2010) were searched for original research and review articles published in English using the terms dexlansoprazole and TAK-390MR. The reference lists of identified articles were reviewed for additional pertinent publications. Abstracts from 2007-2009 American College of Gastroenterology and Digestive Disease Week meetings were searched using the same terms. RESULTS: By irreversibly binding to H(+)K(+)-ATPase, dexlansoprazole inhibits acid production by the parietal cell. Its dual delayed-release formulation provides 2 distinct releases of medication, prolonging the mean residence time compared with lansoprazole (5.56-6.43 vs 2.83-3.23 hours, respectively). In 2 identical Phase III trials of the healing of EE, there were no significant differences in rates of complete healing after 8 weeks between dexlansoprazole 60 and 90 mg once daily and lansoprazole 30 mg once daily. In 2 studies of the maintenance of healing of EE, rates of healing at 6 months were significantly higher with dexlansoprazole 30, 60, and 90 mg once daily compared with placebo (P < 0.001). Patients with nonerosive reflux disease who received dexlansoprazole 30 or 60 mg once daily had significantly more 24-hour heartburn-free days compared with those who received placebo (P < 0.001). Dexlansoprazole was well tolerated compared with placebo or lansoprazole in all studies. CONCLUSIONS: In the studies reviewed, dexlansoprazole was well tolerated and effective in the healing and maintenance of EE, and in the treatment of nonerosive reflux disease. However, most of the available evidence involved comparisons with placebo, making it difficult to draw meaningful conclusions about the place of dexlansoprazole among PPIs. More head-to-head comparative trials with other PPIs are needed to determine whether the unique formulation of dexlansoprazole translates into a clinically meaningful improvement in outcomes.

Spontaneous symmetry breaking during interrupted crystallization of an axially chiral amino acid derivative.

High net enantiomeric excess was observed for crystal collections obtained by crystallization of the TFA salt of a configurationally stable yet racemic axially chiral amidoamine in EtOH solution with or without stirring (up to >99% ee at < or = 15% crystallization).

Rivaroxaban: a novel, oral, direct factor Xa inhibitor.

Thromboembolic disorders such as deep vein thrombosis, pulmonary embolism, myocardial infarction, and stroke often result in long-term disability and/or mortality. The anticoagulants currently available have been effective in the treatment and prevention of these disorders; however, parenteral administration, variable pharmacokinetics and pharmacodynamics, drug and dietary interactions, and a requirement for frequent monitoring of efficacy and safety limit use of these drugs. Rivaroxaban is a novel, oral factor Xa inhibitor in clinical development for the treatment and prevention of thromboembolic diseases. Rivaroxaban is a small molecule directed at active sites, and the agent mechanistically differs from traditional anticoagulants, such as heparins and fondaparinux, in that its activity is independent of antithrombin and its ability to inhibit prothrombinase bound factor Xa. In addition, preclinical and clinical trial data indicate that rivaroxaban has predictable pharmacokinetics and pharmacodynamics, which are features that differentiate it from oral vitamin K antagonists. Phase II studies showed that rivaroxaban is safe and well tolerated across a wide range of doses. Furthermore, completed phase III studies demonstrated its efficacy in the prevention of venous thromboembolism after orthopedic surgery. Additional studies are now under way to evaluate the use of rivaroxaban in the treatment and prevention of other venous and arterial thromboembolic conditions.