2-exo-(6'-methoxycarbonylhexyl)-8-oxabicyclo<3.2.1>oct-6-en-3-one 生成 7-((1R,5S,6R)-2-Hydroxy-4-methoxy-7-oxo-3,9-dioxa-bicyclo[3.3.1]non-6-yl)-heptanoic acid methyl ester 、 7-((1R,5S,6R)-4-Hydroxy-2-methoxy-7-oxo-3,9-dioxa-bicyclo[3.3.1]non-6-yl)-heptanoic acid methyl ester