Enzyme-catalyzed organic syntheses: transesterification reactions of chlorophyll a, bacteriochlorophyll a, and derivatives with chlorophyllase

The green plant enzyme chlorophyllase (EC 3.1.1.14, chlorophyll chlorophyllido-hydroase) has been used for the synthesis of a variety of primary alcohol and diol esters of chlorophyll a, bacteriochlorophyll a, and pyrobacteriochlorophyll a. Green plant chlorophyllase accepts a much larger range of alcohol and chlorophyll substrates than had previously been realized. Thus, chlorophyllide and bacteriochlorophyllide esters of primary alcohols such as retinol and the detergent Triton X-100 and of dihydric alcohols such as ethylene glycol, butanediol, or 2-hydroxyethyl disulfide can readily be obtained by enzyme-assisted transesterification. The diol chlorophyllide esters are valuable intermediates for the synthesis of reaction center special pair models. Chlorophyllase-assisted reactions can be carried out in media containing up to 95% of organic solvents without the concomitant side reactions that important chlorophyll functional groups readily undergo even under mild conditions in conventional chemical synthetic procedures. In competitive chlorophyllase-catalyzed transesterification reactions, long-chain alcohols such as farnesol and retinol vs simple aliphatic alcohols and diols, the enzyme shows a definite preference for the long-chain alcohol. 37 references, 1 figure, 2 tables.