丙酮 、
methyl 2-[(2R,3R,6S)-tetrahydro-2-hydroxy-3-methyl-6-{(1S)-1-methyl-2-oxoprop-1-yl}-2H-pyran-2-yl]glycolate 在
phosphorus pentoxide 作用下,
反应 22.0h,
以69%的产率得到methyl (5S,7S,10R)-2,2,10-trimethyl-7-{(1S)-1-methyl-2-oxoprop-1-yl}-1,3,6-trioxaspiro[4.5]decan-4-carboxylate