Regioselective Synthesis of Benzannulated [5,6]-Oxaspirolactones via Cu(II)-Catalyzed Cycloisomerization of 2-(5-Hydroxyalkynyl)benzoates.

Spiroketals and oxaspirolactones are widely found in biologically active natural products, serving as important structural motifs. In this study, we present a Cu(II)-catalyzed cascade cycloisomerization of 2-(5-hydroxyalkynyl)benzoates, enabling the regioselective synthesis of benzannulated [5,6]-oxaspirolactones containing an isochromen-1-one moiety. This strategy offers a rapid and efficient approach to access a diverse array of benzannulated [5,6]-oxaspirolactones. The methodology presented here showcases a broad substrate scope, delivering good yields and scalability up to gram scale. The structures of the oxaspirolactones were unequivocally confirmed through single-crystal X-ray analysis and by analogy using 1H and 13C{1H} NMR data.

Efficacy of low-level laser therapy in the management of postoperative surgical sequelae after surgical removal of impacted mandibular third molars.

Introduction: The study is aimed to evaluate the effectiveness of low-level laser therapy (LLLT) in the control of pain, swelling, and trismus after the surgical removal of impacted mandibular third molars. Materials and Methods: A prospective study was conducted on thirty patients requiring surgical removal of the impacted mandibular third molar. Mesioangular impacted third molar with class I level B position (according to the Pell and Gregory classification) were included in the study. The study group (n = 15) received LLLT using diode laser of wavelength 980 nm and the control group (n = 15) received routine postoperative care without LLLT. The parameters evaluated were intensity of pain, maximum mouth opening, postoperative swelling, healing at the surgical site, and presence of dry socket. Results: The mean score of pain, swelling, and trismus in the study group were statistically lower as compared to the control groups. Healing assessment using Laury and Turnbull healing index inferred that the healing at the seventh postoperative day was superior in the study group as compared to the control group. Conclusions: LLLT with a diode laser of wavelength 980 nm can effectively reduce pain, swelling, and trismus in the postoperative phase after surgical extraction of the mandibular impacted third molar and promote healing at the operative site.

Ready Access to Benzannulated [5,5]-Oxaspirolactones Using Au(III)-Catalyzed Cascade Cyclizations.

This work showcases an unprecedented Au(III)-catalyzed cascade cyclization of 2-(4-hydroxyalkynyl)benzoates to access benzannulated [5,5]-oxaspirolactones related to biologically active natural products. This reaction proceeds through an initial 5-endo-dig mode of hydroalkoxylation of the alkynol segment to give the oxocarbenium species (via cyclic enol-ether) followed by the addition of carboxylate onto the oxocarbenium that delivers the oxaspirolactone scaffold. While testing this method's scope, we found that the steric and electronic environment of the hydroxyl group could alter the reaction pathway that delivers isochromenone through a competitive 6-endo-dig mode of attack of the carboxylate onto the tethered alkyne.

Stereoselective Total Synthesis of (±)-Pleurospiroketals A and B.

A full account of our efforts toward the stereoselective total synthesis of sesquiterpenoid-derived natural products (±)-pleurospiroketals A and B is described. Commercially available 3-methyl-2-cyclohexenone and 2,2-dimethyloxirane were used as key building blocks, and the substrate-controlled stereoselection was exploited to access the entire stereochemistry of these natural products. Initially, a planned synthetic route involving a [6,5]-bicyclic lactone intermediate was found to be insurmountable, and the later strategy comprising OsO4-NMO-mediated dihydroxylation of 3-methyl-2-cyclohexenone, followed by Luche reduction, Eschenmoser methylenation, and Brønsted acid-induced spiroketalization steps, was ultimately identified as the reliable strategy.

Uncontrolled bleeding during tooth extraction from an undiagnosed arteriovenous malformation.

Arteriovenous malformations (AVMs) are rare congenital disorders of vascular morphogenesis. These lesions are characterised by high vascular flow with risk of severe bleeding from accidental trauma or surgical manipulation. Although infrequent, potentially life-threatening and fatal oral bleeding has been reported during extraction of tooth associated with AVM. This paper presents a case of uncontrolled bleeding in an adult female patient undergoing mandibular anterior tooth extraction. The bleeding was related to undiagnosed soft tissue AVM in gingivobuccal space. Management of the case with review of previously reported similar cases is presented.

Recent advances in the synthesis of oxaspirolactones and their application in the total synthesis of related natural products.

Oxaspirolactones are ubiquitous structural motifs found in natural products and synthetic molecules with a diverse biochemical and physicochemical profile, and represent a valuable target in natural product chemistry and medicinal chemistry. Since the 1970s, numerous innovative synthetic methodologies have been reported for these scaffolds in the context of expanding the range of potential building blocks, catalysts, and modes of transformations (racemic or asymmetric protocols). This review focuses on a broad spectrum of approaches toward the synthesis of oxaspirolactones and their potential application in the total synthesis of biologically relevant natural products starting from the first disclosure to the latest report.

Synthesis of Furo[2,3-b]pyran-2-ones through Ag(I)- or Ag(I)-Au(I)-Catalyzed Cascade Annulation of Alkynols and α-Ketoesters.

Ag(I)- or Ag(I)-Au(I)-catalyzed cascade annulation of alkynols (5-hexyn-1-ol systems) with α-ketoesters involving a dual activation process (π and σ) has been developed for the first time. This reaction proceeds through cycloisomerization of alkynol to give the 6-endo-enol ether followed by annulation with an α-ketoester to furnish furo[2,3-b]pyran-2-ones in good yields. Chemical structures of all products were rigorously confirmed by single crystal X-ray analysis and analogy.

Four-Step Total Synthesis of (+)-Yaoshanenolides A and B.

A highly concise bioinspired four-step total synthesis of yaoshanenolides A and B possessing tricyclic spirolactone with an unusual 5'H-spiro-[bicyclo[2.2.2]-oct[2]ene-7,2'-furan]-5'-one scaffold is reported. This synthesis features high-yielding aldol-type addition of γ-butyrolactone on to the aldehyde, exocyclic olefination of lactone derivative using Eschenmoser's salt, and highly facial- and endo-selective [4 + 2]-cycloaddition of fully functionalized 5-methylene-2(5H)-furanone with natural R-(-)-α-phellandrene. The approach allows access to yaoshanenolides A and B in four linear steps in 11 and 13% overall yield.

Lewis acid catalyzed cascade annulation of alkynols with α-ketoesters: a facile access to γ-spiroketal-γ-lactones.

A novel Lewis acid catalyzed intermolecular cascade annulation of alkynols with α-ketoesters has been developed. This simple and efficient cascade annulation proceeds through a 5-exo-dig cyclization of alkynols followed by annulation with α-ketoester to provide a wide variety of unsaturated γ-spiroketal-γ-lactones (1,6-dioxaspiro[4.4]non-3-en-2-ones) related to many natural products.