Engineering acyclic stereocontrol in the alkylation of vinylglycine-derived dianions: asymmetric synthesis of higher alpha-vinyl amino acids.

ABSTRACT: A generalizable synthesis of higher L-alpha-vinyl amino acids is presented. The strategy pursued here involves the introduction of the amino acid side chain via the alkylation of a chiral, vinylglycine-derived dianionic dienolate, bearing the (-)-8-(beta-naphthyl)menthyl (d'Angelo) auxiliary. A model is presented that postulates a favored "exo-entended" conformation for this dienolate, leading to C(alpha)-alkylation at the si face. The model invokes internal amidate chelation to control ester enolate geometry and soft-soft interactions between the polarizable beta-naphthyl ring of the auxiliary and the extended pi-system of the dienolate to shield the re face. Heats of formation for four conformers of this dianion were calculated for their semiempirical optimized geometries (PM3). The resu

SUBMITTER: Berkowitz DB 

PROVIDER: S-EPMC6054771 | biostudies-literature | 2000 May

REPOSITORIES: biostudies-literature