Enzymatic optical resolution of dibenzoxepins and its application to an optically active antiallergic agent with thromboxane A2 receptor antagonistic activity.

Methyl (+/-)-11-(2-hydroxyethyl)thio-6,11-dihydrodibenz[b,e]oxepin- 2- carboxylate (5) was enantio-selectively acylated with acetic anhydride in an organic medium by Lipase Amano P to give methyl (-)-11-(2-acetoxyethyl)thio-6,11-dihydrodibenz[b,e]oxepin-2- carboxylate (8), and the (+)-enantiomer by Lipase Sigma Type VII. Using Lipase Amano P, (+)- and (-)-(5) could be prepared with high optical purity (84-94% e.e.). These products were respectively converted to (+)- and (-)-KW-4099, which had antiallergic activity with complete retention of the optical purity.