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Starting from dimethyl (E)-2-{[(1-tert-butoxycarbonyl)-1H-indol-3-yl]methylene}succinate and (R)-2,2,5,5-tetramethyl-1,3-dioxolane-4-carbaldehyde, facile synthesis of (-)-epi-claulansine D was accomplished via condensation and two intramolecular cyclizations. The (-)-epi-claulansine D in the solid state exists in a metastable form, and after an induction period of 30-90 days, it underwent complete epimerization to exclusively deliver the desired natural product (-)-claulansine D in quantitative yield. The witnessed inversion of C-centrochirality in the solid state is conceptually novel and takes place for relatively higher crystal stability reasons. Base-catalyzed ring expansion of both (±)/(-)-epi-claulansine D and (±)/(-)-claulansine D resulted in (±)/(+)-epi-claulansine C in very good yields. [ABSTRACT FROM AUTHOR]

The common precursor 1-methoxy-2-prenyl-3-carbomethoxycarbazole was synthesized from dimethyl indolylmethylenesuccinate in four steps. Well-planned reductive and/or oxidative transformations and intramolecular cyclizations were performed on a pivotal common precursor to accomplish collective first total synthesis of titled natural products and proposed claulamine E. Burgess reagent induced formation of kinetically controlled product claulamine A, and intramolecular cyclizations to form bicyclic claulansine A were the key reactions. An alternatively attempted synthesis failed to provide the structural isomer of proposed claulamine E. [ABSTRACT FROM AUTHOR]

Facilesyntheses of imperative carbazole alkaloids carbazomycinA, carbazomycin B, hyellazole, chlorohyellazole, and clausenalineD have been demonstrated starting from readily available Boc-protected3-formylindole and dimethyl maleate. The suitably substituted aromaticrings have been designed comprising three/four significant C–Cbond forming reactions. The competent Wittig reaction, selective monoalkylations,one-pot regioselective Weinreb amide formation and Boc-deprotection,well designed Grignard reactions, dehydrative intramolecular cyclizations,and Baeyer–Villiger rearrangement of aromatic aldehydes werethe main features. [ABSTRACT FROM AUTHOR]

We describe an enantioselective synthesis of (3 R ,3 aS ,6 aR )-hexahydrofuro[2,3- b ]furan-3-ol which is a key subunit of darunavir, a widely used HIV-1 protease inhibitor drug for the treatment of HIV/AIDS patients. The synthesis was achieved in optically pure form utilizing commercially available sugar derivatives as the starting material. The key steps involve a highly stereoselective substrate-controlled hydrogenation, a Lewis acid catalyzed anomeric reduction of a 1,2- O -isopropylidene-protected glycofuranoside, and a Baeyer-Villiger oxidation of a tetrahydrofuranyl-2-aldehyde derivative. This optically active ligand alcohol was converted to darunavir efficiently.