Chiral enzymatic cascade reactions

Apart from ATRP, the concept of dual initiation was also applied to other (controlled) polymerization techniques. Nitroxide-mediated living free radical polymerization (LFRP) is one example reported by van As et al. and has the advantage that no further metal catalyst is required [43], Employing initiator NMP-1, a PCL macroinitiator was obtained and subsequent polymerization of styrene produced a block copolymer (Scheme 4). With this system, it was for the first time possible to successfully conduct a one-pot chemoenzymatic cascade polymerization from a mixture containing NMP-1, CL, and styrene. Since the activation temperature of NMP is around 100 °C, no radical polymerization will occur at the reaction temperature of the enzymatic ROP. The two reactions could thus be thermally separated by first carrying out the enzymatic polymerization at low temperature and then raising the temperature to around 100 °C to initiate the NMP. Moreover, it was shown that this approach is compatible with the stereoselective polymerization of 4-MeCL for the synthesis of chiral block copolymers. 

Moore et al. reported the first in vitro assembly of a complete type 11PKS enzymatic pathway and demonstrated the multienzyme total synthesis of the bacteriostatic agent enterocin [53], They employed nine recombinant and three commercial proteins in a single reaction vessel along with the necessary cofactors (S-adenosyl-L-methionine (SAM), ATP, Mg +, and NADPH) to produce enterocin (51) from its primary metabolite precmsors (benzoic acid and malonyl-CoA) (Scheme 15.16). This remarkable enzyme cascade generates 10 C-C bonds, 5 C-O bonds, and 7 chiral centers in impressive 25% yield. 

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