Atropo- and Diastereoselective Construction of Tetracyclic Biphenylazepinium Salts Derived from Aminoalcohols: Use as Catalysts in Enantioselective Asymmetric Epoxidation.

A range of new biphenylazepinium salt organocatalysts effective for asymmetric epoxidation has been developed incorporating an additional substituted oxazolidine ring, and providing improved enantiocontrol in alkene epoxidation over the parent structure. Starting from enantiomerically pure aminoalcohols, tetracyclic iminium salts were obtained as single diastereoisomers through an atroposelective oxazolidine formation.

Short and versatile route to a key intermediate for lactacystin synthesis.

[reaction: see text] A key intermediate 14 for the synthesis of lactacystin 1 has been constructed in four steps and 33% overall yield. The key steps involve cyclization of a suitably functionalized glutamic acid derivative and concomitant alkylation of the resulting beta,beta-diketoester system, C-acylation of the cyclic alpha-amidoketone 9, and decarboxylbenzylation of 12. Alkylation of a related beta,beta-diketoester 5 was additionally achieved with several electrophiles.