Portal de Periódicos da CAPES

Optically active imidazole‐containing polymers

1968; Inderscience Publishers; Volume: 6; Issue: 10 Linguagem: Inglês

10.1002/pol.1968.150061005

1542-9350

C. G. Overberger, Iwhan Cho,

Chemical Reactions and Mechanisms

Abstract In order to investigate the stereospecificity of enzyme‐catalyzed reactions, an optically active copolymer of 4(5)‐vinylimidazole and 2,5( S )‐dimethyl‐1‐hepten‐3‐one was synthesized, and its effects on the solvolytic rates, in ethanol‐water, of the p ‐nitrophenyl and 4‐carboxy‐2‐nitrophenyl esters of 3( R )‐ and 3( S )‐methylpentanoic acid and of the commercially available N ‐carbobenzoxy‐( R )‐ and ( S )‐phenylalanine p ‐nitrophenyl esters were investigated. The optically active comonomer was prepared by thermal decomposition of solid (+)‐1‐piperidino‐2,5( S )‐dimethylheptan‐3‐one hydrochloride, which was obtained from the reaction of 2( S )‐methylbutyllithium with 3‐piperidino‐2‐methylpropionitrile. The 3( R )‐methylpentanoic acid was prepared in 92% optical purity from L ‐alloisoleucine via diazotization in concentrated hydrobromic acid and subsequent reductive debromination with zinc amalgam in dilute hydrochloric acid. In the optically active copolymer‐catalyzed solvolyses of the optically active esters performed at pH values of 6–8 no significant differences between the solvolytic rates of ( R ) and ( S ) isomers of substrates were observed. Poly‐ L ‐histidine was also employed as a catalyst for the solvolyses of these substrates. At pH 6.0 in ethanol–water the latter catalyst also failed to exhibit specificity towards ( R ) and ( S ) substrates.