C-Alkynylation of Cyclopropanols.

Alkynylation of cyclopropanols with 1-bromo-1-alkynes has been devised for easy access to synthetically useful alk-4-yn-1-ones. This method broadens the utility of attractively functionalized cyclopropanols as a new class of homoenolate equivalent in C-C bond formation.

Concise synthesis of alkaloid (-)-205B.

Described herein is a short total synthesis of alkaloid (-)-205B (1) by means of an anti-selective SN2' alkylation of an attractively functionalized cyclopropanol and diastereoselective cyclization of the resulting aminoallene adduct for bicyclic ring formation. The synthesis features a general route to cis- or trans-2,6-disubstituted piperidines by lithium aluminum hydride reduction of the imine intermediate by an appropriate choice of solvent and cis- or trans-2,5-disubstituted pyrrolidines by an exceptional level of chirality transfer from a pendant allene. Particularly noteworthy are the brevity and convergence made possible by a segment-coupling strategy.

Cross-coupling of cyclopropanols: concise syntheses of indolizidine 223AB and congeners.

A new synthetic method for indolizidine or pyrrolizidine alkaloids based on readily available and attractively functionalized cyclopropanols, as exemplified in concise syntheses of indolizidine (-)-223AB, its 3-epimer, (-)-indolizidine 239AB, and (-)-indolizidine 239CD, is reported. This work highlights the applications of SN2' alkylation and C-acylation of cyclopropanols to meet stereochemical challenges in natural product synthesis. Also included is diastereoselective cyclization of the resulting aminoallene adduct for bicyclic ring formation.

Total synthesis and revision of the absolute configuration of seimatopolide B.

The asymmetric total synthesis of natural seimatopolide B along with its enantiomer is described starting from readily available 5-hexen-1-ol and 3-buten-1-ol. The key steps involved are Jacobson hydrolytic kinetic resolution, proline-catalyzed α-hydroxylation, Yamaguchi esterification and ring-closing metathesis. This asymmetric total synthesis necessitates the revision of the originally assigned (3R, 6S, 9S)-configuration to (3S, 6R, 9R).

Synthesis of the macrocyclic core of iriomoteolide 3a.

The asymmetric synthesis of the fully functionalized macrocyclic core of iriomoteolide 3a, a cytotoxic 15-membered macrolide, is disclosed. The key steps involve Sharpless asymmetric dihydroxylation, Sharpless asymmetric epoxidation, olefin cross-metathesis, Yamaguchi esterification, and a ring-closing metathesis reaction for macrocyclization.