Biocatalytic acylation of Efavirenz intermediate: Unexpected novel product formation

During attempted biocatalytic resolution of (R/S)-5-chloro-α-(cyclopropylethynyl)-2-amino-a-(trifluoromethyl) benzenemethanol containing a tertiary hydroxyl group, a novel, unexpected benzoxazine derivative (Efavirenz analogue) is formed during the lipase B from Candida antarctica (Novozyme -435) catalyzed reaction of Efavirenz intermediate (R/S)-5-chloro-α-(cyclopropylethynyl)-2-amino-α-(trifluoromethyl) benzenemethanol 1 using vinyl acctate.