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The polyesterification of adipic acid and butane-l,4-diol by a commercial lipase (Lipozyme IM-20) has been studied using a two-chamber reactor and molecular sieve as a dehydrating agent. The lower oligomeric products were identified and a low-dispersity polyester averaging 20 repeat units was produced.

upon Tyne NEI 7RU As a result of methylation, benzoylation, and other chemical experiments, as well as of studies of the conversion into melanin of samples of dopamine specifically labelled with deuterium at each of the a-, p-, 2-, 5-, and 6-positions (separately), a preliminary outline structure is put forward to represent autoxidative dopamine-melanin. This melanin differs considerably from autoxidative dopa-melanin ; in particular, it is suggested that N-C polymeric linkages may be important, and that more uncyclised side chains are present than in dopa-melanin.

Preliminary enzymatic polymerization studies in the simple stoichiometric adipic acid/butane‐1,4‐diol system using lipase B from Candida antarctica, immobilized as Novozym 435®, suggest that in solvent‐free conditions a step‐growth mechanism operates involving the sequential addition of an AB synthon by esterification mode only. Conversely, in toluene as solvent there is a change to the more facile transesterification mode in line with the conventional polyesterification procedure, pointing to a change in specificity of the lipase. Evidence is drawn from qualitative studies using a series of synthetic intermediates, enabling authentication of product mixtures together with an indication of the comparative reactivity of species along the proposed reaction pathway. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2069–2080, 1998

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