A facile new procedure for the deprotection of allyl ethers under mild conditions

A novel isomerization of O-allyl glycosides into prop-1-enyl glycosides was observed instead of cross-metathesis during an olefin metathesis reaction using Grubbs' ruthenium benzylidene catalyst (Cy3P)(2)RuCl2=CHPh (1), N-all yltritylamine, and N,N-diisopropylethylamine as necessary auxiliary reagent s. In the search for a better catalytic system, it has been found that dich lorotris(triphenylphosphine)ruthenium(II), [(C6H5)(3)P](3)RuCl2, (2) was mu ch more efficient for the isomerization of allylic ethers. The labile prop- 1-enyl group was easily hydrolyzed using HgCl2-HgO and the hemiacetals (25- 32) were isolated in excellent yields (ca. 90%).