Premium
Synthesis and polymerization of benzyl (3R,4R)‐3‐methylmalolactonate via enzymatic preparation of the chiral precursor
Author(s) -
Bear MarieMaud,
Monne Claire,
Robic Daniel,
Campion Geneviève,
Langlois Valérie,
Rimbault Alain,
Bourbouze Richard,
Guerin Philippe
Publication year - 1998
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/(sici)1520-636x(1998)10:8<727::aid-chir2>3.0.co;2-q
Subject(s) - chemistry , hydrogenolysis , enantiomeric excess , polymerization , enantiomer , chirality (physics) , catalysis , polymer , stereochemistry , substrate (aquarium) , organic chemistry , enantioselective synthesis , chiral symmetry , nambu–jona lasinio model , physics , oceanography , quantum mechanics , quark , geology
β‐methylaspartate ammonia‐lyase, EC 4.3.1.2, (β‐methylaspartase) from Clostridium tetanomorphum was used to produce a 40/60 molar ratio of (2S,3R) and (2S,3S)‐3‐methylaspartic acids, 2a and 2b , respectively, from mesaconic acid 1 as substrate, on a large scale. To prepare (3R,4R)‐3‐methyl‐4‐(benzyloxycarbonyl)‐2‐oxetanone (benzyl 3‐methylmalolactonate) 6, 2a and 2b were transformed, in the first step, into 2‐bromo‐3‐methylsuccinic acids 3a and 3b and separated. After three further steps, (2S,3S)‐ 3a yielded the α,β‐substituted β‐lactone (3R,4R) 6 with a very high diastereoisomeric excess (>95% by chiral gas chromatography). The corresponding crystalline polymer, poly[benzyl β‐(2R,3S)‐3‐methylmalate] 8 , prepared by an anionic ring opening polymerization, was highly isotactic as determined by 13 C NMR. Catalytic hydrogenolysis of lactone 6 yielded (3R,4R)‐3‐methyl‐4‐carboxy‐2‐oxetanone (3‐methylmalolactonic acid) 7 , to which reactive, chiral, or bioactive molecules can be attached through ester bonds leading to polymers with possible therapeutic applications. Because of the ability of β‐methylaspartase to catalyse both syn‐ and anti‐elimination of ammonia from (2S,3RS)‐3‐methylaspartic acid 2ab at different rates, the (2S,3R)‐stereoisomer 2a was retained and isolated for further reactions. These results permit the use of the chemoenzymatic route for the preparation of both optically active and racemic polymers of 3‐methylmalic acid with well‐defined enantiomeric and diastereoisomeric compositions. Chirality 10:727–733, 1998. © 1998 Wiley‐Liss, Inc.