Synthesis of cis-4-(phosphonooxy)-2-piperidinecarboxylic acid, an N-methyl-D-aspartate antagonist

An Efficient synthesis of orthogonally protectedtrans- andcis-4-aminopipecolic acid

“…The known synthetic pathway was applied to obtain 2 from 4-bromo-1-butene (1, Scheme I) [10][11][12].…”

Practical, Stereoselective Synthesis of Palinavir, a Potent HIV Protease Inhibitor

“…18 Recently, we published a route to such derivatives (Scheme 4), 18a which is based on an asymmetric version of an iminium ion cyclization originally developed by Hays. 19 A simple procedure relying on the selective crystallization of diastereomeric salts was used to provide lactone 17a of high isomeric purity (93.4%) and 27-29% overall yield from 16, without the need for chromatography. Lactone 17a is a useful synthetic intermediate for the preparation of a variety of 4-substituted pipecolic acid derivatives in isomerically pure form, including fragment 8.…”

An Aza-Prins Cyclization Approach to Functionalized Indolizidines from 2-Allylpyrrolidines

“…The formation of lactone 12a may be rationalized by ring closure of the olefin in 10a onto the iminium ion followed by nucleophilic interception of the resulting carbocation by the carboxyl group in glyoxylic acid. 16 In like manner, the reactions of 2-allypyrrolides 10b and 10c under similar conditions gave indolizidine lactones 12b and 12c in good yields (97% and 83%, respectively) as single diastereomers. Spectroscopic analysis of indolizidine 12a revealed that the newly formed lactone ring in 12a adopts a syn -1,3-diaxial conformation with respect to the indolizidine system.…”