Benzo b thiophen-5-yl derivative and process for producing the same.

摘要

This invention relates to a process for producing a compound represented by formula (6a) or (6b): or wherein R<2> represents a hydrogen atom or a hydroxyl-protecting group and R<4> and R<5>, which may be the same or different, represent lower alkyl groups, using a compound represented by formula (2a) or (2b) obtained by preferential crystallization: or and also to a compound represented by the following formula (7) which is an intermediate useful for producing the compound of formula (6a) or (6b): wherein R<1> represents a group represented by formula (8): wherein R<2> is as defined above and R<3> represents a hydrogen atom or a hydroxyl-protecting group, a group represented by the formula (9): or a group represented by formula (10): wherein R<2> is as defined abovef