摘要:
Both enantiomers of calycotomine (R)-5 and (S)-5 were prepared through the CAL-B-catalysed asymmetric O-acylation of N-Boc-protected (6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolin-1-yl)methanol [(+/-)-3)]. The optimum conditions for the enzymatic resolution were determined under continuous-flow conditions, while the preparative-scale resolution of (+/-)-3 was performed as a batch reaction with high enantiselectivity (E>200). The resulting amino alcohol (S)-3 and amino ester (R)-4, obtained with high enantiomeric excess (ee = 99%), were transformed into the desired calycotomine (S)-5 and (R)-5 (ee = 99%). A systematic study was carried out in a continuous-flow system on the O-acylation of tetrahydroisoquinoline amino alcohol homologues (+/-)-1 to (+/-)-3 containing a remote stereogenic centre. (C) 2013 Elsevier Ltd. All rights reserved.