Enzymes in organic synthesis. 27. Lipase-Catalyzed Synthesis of (5R,6S)-6-Acetoxyalkan-5-olides - homologues of the mosquito oviposition attractant pheromone
摘要:
Sixteen homologous (5R*,6S*)-6-hydroxyalkan-5-olides rac-5 and their acetoxy derivatives rac-6 were synthesized from the corresponding methyl (Z)-alk-5-enoates 3 by osmium(VIII) oxide catalyzed cis-hydroxylation to the dihydroxy esters rac-4 and hydrolysis of these esters followed by lactonization. Pancreatin-catalyzed lactonization of the dihydroxy esters rac-4 afforded enantiomerically enriched hydroxy lactones ent-5, five of which were obtained enantiomerically pure by recrystallization. Acetylation of the 6-hydroxyalkan-5-olides rac-5 by vinyl acetate catalyzed by the lipase SP 526 provided enantiomerically enriched 6-acetoxyalkan-5-olides 6 with an enantiomeric excess of more than 90% in nine cases. These compounds are known as mosquito oviposition attractant pheromone (6h) or its homologues.
Les groupes anioniques et nucleophiles sur la chainelaterale desylures de triphenylphosphonium provoquent un deplacement de lastereochimie de l'alcene obtenu vers l'isomere trans dans les 反应 avec des 醛。L'effet est souvent 加上重要的 avec des aldehydes aromatiques qu'avec des aldehydes aliphatiques。氧、羧酸、氨基和酰胺基的取代基研究