摘要：

In this article, we report the first stereochemical study of an enzymatic 1,4-dehydrogenation reaction, namely, the transformation of ( Z )-11-tetradecenoic acid into ( E , E )-10,12-tetradecadienoic acid, involved in the sex pheromone biosynthesis of the moth Spodoptera littoralis . The investigation was carried out using the labeled substrates ( R )-[10- 2 H]- and ( S )-[10- 2 H]-tridecanoic acids (( R )- 2 and ( S )- 2 , respectively) and ( R )-[2,2,3,3,13- 2 H 5 ]- and ( S )-[2,2,3,3,13- 2 H 5 ]-tetradecanoic acids (( R )- 1 and ( S )- 1 , respectively). Probes ( R )- 2 and ( S )- 2 were prepared as described in a previous article. 1 The synthesis of the pentadeuterated chiral substrates ( R )- 1 and ( S )- 1 was accomplished by kinetic resolution of the racemic 12-tridecyn-2-ol ( 6 ) with immobilized porcine pancreatic lipase. The enantiomerically pure alcohols ( R )- 6 and ( S )- 6 were transformed into the final acids ( S )- 1 and ( R )- 1 , respectively, by a sequence of well-established reactions. The analyses of methanolyzed lipidic extracts from glands incubated separatedly with each individual probe showed that in the transformation of ( Z )-11-tetradecenoic acid into ( E , E )-10,12-tetradecadienoic acid, both pro -( R ) hydrogen atoms at C-10 and C-13 are removed from the substrate. This is the first example reported of a desaturase with pro -( R )/ pro -( R ) stereospecificities that gives rise to ( E )-double bonds. A mechanistic explanation for the stereochemical outcome of this reaction is advanced.

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