Total synthesis of (+)-conagenin

The total synthesis of the immunomodulator, (+)-conagenin was achieved using, as a key step, a method developed by us for the synthesis of 2-methyl-1,3-diols via Ti(III)-mediated diastereo- and regioselective opening of trisubstituted 2,3-epoxy alcohols, to carry out the stereoselective construction of its pentanoic acid segment

Synthesis of C6-substituted 3,4-dideoxy furanoid sugar amino acids

A variety of chiral 3,4-dideoxy furanoid sugar amino acids have been synthesized, which were substituted at C6 with different alkyl groups, such as methyl, benzyl, isopropyl and hydroxymethyl synthesized from their corresponding N,N-dibenzylaminoaldehydes

Total Synthesis of Varitriol, Varioxirane, and Enantiomer of the Proposed Biosynthetic Precursor

The first stereoselective total synthesis of varioxirane was accomplished, and the proposed biosynthetic pathway was supported by converting varioxirane to (+)-varitriol. The first total synthesis of enantiomer of the proposed biosynthetic precursor, (1<i>E</i>,3<i>S</i>,4<i>R</i>,5<i>E</i>)-1-(2-(hydroxymethyl)-3-methoxyphenyl)­hepta-1,5-diene-3,4-diol, was also achieved by utilizing the unreacted allylic alcohol obtained during the Sharpless kinetic resolution step. Other key steps include the Horner–Wadsworth–Emmons reaction and the diastereoselective reduction of α,β-unsaturated ketone to its corresponding alcohol

Total Synthesis and Absolute Configuration of Curvularides A‑E

The first total synthesis of curvularides A–E, isolated from a culture broth of the endophytic fungus <i>Curvularia geniculata</i>, is described. The divergent total synthesis reported herein confirmed the absolute configurations of curvularides A–E and supported that these natural products might be obtained from a common biosynthetic pathway. The key steps involved in the synthesis were the diastereoselective hydrogenation of <i>exo</i>-methylene-γ-butyrolactone to α-methyl-γ-butyrolactone, Sharpless kinetic resolution, Sharpless asymmetric epoxidations, and intramolecular and intermolecular epoxide openings

Nazarov Cyclization and Tandem [4 + 2]-Cycloaddition Reactions of Donor–Acceptor Cyclopropanes

The development of aryl vinyl/divinyl donor–acceptor cyclopropanes (DACs) as novel Nazarov cyclization (NC) precursors is described. The 1,3-zwitterion, generated from DACs embedded in the divinyl framework, acts as a pentadienyl cation, a requisite for Nazarov cyclization. A cyclic allyl cation in the course of NC was trapped with external nucleophiles to provide an interrupted NC product. Indeed, an allyl cation in this reaction is analogous to a 1,4-zwitterion that on reaction with dipolarophiles provided an easy access to substituted pyrans with excellent yield and diastereoselectivity via NC followed by a formal [4 + 2] cycloaddition

Stereoselective Access to the Core Structure of Macroline-Type Indole Alkaloids: Total Synthesis of Macroline and Alstomicine

Rapid synthesis of the pentacyclic core structure of macroline-type indole alkaloids, and its application in the total synthesis of macroline and alstomicine is described. The core structure was accomplished in a highly stereocontrolled manner via two key steps, Ireland–Claisen rearrangement and Pictet–Spengler cyclization, commencing from a readily available starting material l-tryptophan, which obviated the need of a particular chiral source as an external catalyst, reagent, or internal auxiliary