An efficient total synthesis of (+/-)-lycoramine.

[reaction: see text] A short and unique approach to (+/-)-lycoramine as one of the galanthamine-type alkaloids has been efficiently developed. The alternative advantage lies in that three stereocenters, including a crucial quaternary carbon center, were constructed with high diasteroselectivity via a key one-step NBS-mediated semipinacol rearrangement of the allylic alcohol.

Progressive studies on the novel samarium-catalyzed diastereoselective tandem semipinacol rearrangement/Tishchenko reduction of secondary alpha-hydroxy epoxides.

A novel and highly diastereoselective samarium-catalyzed tandem rearrangement/reduction of secondary alpha-hydroxy epoxides, which involves a C1 to C3 carbon migration rearrangement and a very interesting hetero-Tishchenko reduction of the intermediate aldehyde and the reductant aldehyde, has been reported. This reaction could be developed to provide a facile and stereoselective construction of 2-quarternary 1,3-diol units with an hydroxymethyl moiety attached to the diastereogenic quaternary carbon center. Detailed investigations have been carried out concerning the screening of the aldehydes as a reductant, the optimization of reaction conditions, and the substrate scope of this tandem reaction. A catalytic cycle for this reaction, the electronic and steric effects of the reductant aldehydes, and the mechanism for the acyl migration of 1,3-diol monoesters are proposed.

A general efficient strategy for cis-3a-aryloctahydroindole alkaloids via stereocontrolled ZnBr(2)-catalyzed rearrangement of 2,3-aziridino alcohols.

A short and general approach to the cis-3a-aryloctahydroindole alkaloids has been developed on the basis of a key stereocontrolled ZnBr(2)-catalyzed rearrangement of 2,3-aziridino alcohols. Two representative members, (+/-)-crinane and (+/-)-mesembrine, have been synthesized in 15% and 11% overall yields, respectively. [reaction: see text]

Lewis acid promoted highly stereoselective rearrangement of 2,3-aziridino alcohols: a new efficient approach to beta-amino carbonyl compounds.

A new Lewis acid promoted rearrangement reaction of 2,3-aziridino alcohols was discovered, which involved the highly stereoselective construction of a diastereogenic quaternary carbon center and efficient formation of beta-amino carbonyl compounds in excellent yields. A wide variety of Lewis acids were proved to be effective for the reaction, and a possible reaction mechanism was also discussed.

Samarium-Catalyzed Tandem Semipinacol Rearrangement/Tishchenko Reaction of α-Hydroxy Epoxides: A Novel Approach to Highly Stereoselective Construction of 2-Quaternary 1,3-Diol Units.

Three contiguous stereocenters are constructed with high diastereoselectivity in a novel samarium-catalyzed tandem reaction of α-hydroxy epoxides 1 to give exclusively the C1,C2-anti isomers of 2 and 2'. This could lead to the development of a general procedure for the diastereoselective construction of 2-quaternary 1,3-diol units.