CAL-B (Novozym 435) plays a dual role in our approach to chiral polyamides. It is used to introduce the appropriate chirality in the synthesis of monomers (amino-esters and diamines) from racemic 12-methyldodecalactone and then to catalyze their polycondensation. The AB and AABB enzymatic polymerizations have been carried out under reduced pressure; they give rise to optically active polymers in good yield, with a good degree of polymerization, and a narrow polydispersity index. This approach demonstrates that the presence of a methyl group at the stereogenic center at the alpha-position relative to the nitrogen atom does not slow down the polymerization as compared with the polycondensation of a related achiral monomer. (c) 2012 Elsevier Ltd. All rights reserved.
Synthesis of Both Enantiomers of Four Different Macrocyclic Lactones
摘要:
Both enantiomers of macrocyclic lactones, 12-tridecanolide (1), 13-tetradecanolide (2), 14-pentadecanolide (3) and 15-hexadecanolide (4), were synthesized utilizing (S)-(-)-beta-hydroxythioacetal (5) as the chiral building block. Key steps are the C-alkylation of a dianion derived from 5 with alkyl dibromides followed by conversion of functional groups and the two macrolactonization. The both enantiomers of 1 similar to 4 have been obtained by reductive desulfurization of the dithiane moiety.