Di-n-butyltin Oxide

1. in sugar chemistry, equatorial OH of a cis-diol (6 membered sugar) can be selectively protected by BuSnO then benzylbromide/allylbromide in dmf.

2. axial OH of a cis-diol can be oxidized by (BuSnO/MeOH then BuSnOMe/Br2) to ketone selectively.