(R)-2-{(S)-[(R)-2,2-dimethyl-1,3-dioxolan-4-yl]-hydroxy-methyl}-6-hydroxy-3-oxo-3,6-dihydro-2H-pyridine-1-carboxylic acid benzyl ester 在
4 A molecular sieve 、
对甲苯磺酸 作用下,
以
甲苯 为溶剂,
反应 1.5h,
以80%的产率得到(1R,5S,7S)-7-[(R)-2,2-dimethyl-1,3-dioxolan-4-yl]-2-oxo-6-oxa-8-aza-bicyclo[3.2.1]oct-3-ene-8-carboxylic acid benzyl ester