CAL-B catalyzed regioselective bulk polymerization of l-aspartic acid diethyl ester to α-linked polypeptidesElectronic supplementary information (ESI) available: Experimental procedures, 1D 1H NMR of poly(Et-l-Asp) in DMSO-d6, 1D 13C NMR, 2D 1H-1H COSY, 2D 1H-13C HSQC, monomer conversion vs. reaction time, DPavgvs. monomer conversion, DPavg and conversion vs. enzyme loading, TGA and DSC analysis. See DOI: 10.1039/c7cc01300k

This paper reports that the bulk polymerization of l -aspartic acid diethyl ester catalyzed by immobilized CAL-B at 80 °C for 24 h gives primarily (∼95%) α-linked poly( l -aspartate) in 70% yield with DP avg = 50 and regioselectivity (α/β) = 94 : 6. Plots of log{[M] 0 /[M] t } vs. time and DP avg vs. conversion indicate that this polymerization proceeds in a controlled manner by a chain-growth mechanism up to 90% conversion. Thereafter, competition occurs between chain growth and step mechanisms. This paper reports that the bulk polymerization of l -aspartic acid diethyl ester catalyzed by immobilized CAL-B at 80 °C for 24 h gives primarily (∼95%) α-linked poly( l -aspartate) in 70% yield with DP avg = 50 and regioselectivity (α/β) = 94 : 6.