Enantioselective diacyl donors

Early studies on KRP focused on the enantioselective condensation polymerization of an activated chiral diacyl donor (21) with achiral diols such as 22 (Scheme 11.6a) [29]. Lipases of different origin were tested and the formation of optically active trimers and pentamers was demonstrated for the dibromo monomer. The isolated oligomers were end capped with free hydroxy groups and showed small optical rotation values ([a]D25 +4.5 and +4.3 for the trimer and pentamer, respectively). Similarly, the condensation polymerization of achiral diacyl donors 23 with diastereomeric mixtures of chiral diols (24) was shown as well, affording optically active oligomers (Scheme 11.6b) [29]. 

Scheme 11.6 First examples of enantioselective lipase-catalyzed oligomerization of (a) a diastereomeric chiral diacyl donor with a diol and (b) achiral diacyl donors with...

Scheme 11.7 Enantioselective porcine pancreatic lipase (PPL) catalyzed polymerization of chiral diacyl donor 25.

The modified Backvall system was three times faster than the original system and gave similar yields and enantioselectivity for a series of amine and diamine substrates. Attempts to polymerize a chiral diamine with a diacyl donor using... 

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