Question

this is an organic chemistry synthesis question, and I am having a little bit of trouble getting started. Any help with the mechanism would be appreciated! thanks!

2. The following reactions are from an article published by Masamune and Sharpless in Science, describing stereoselective synthesis of hexose sugars. a) The following conversion requires two reaction steps, the second one being protection of a diol as a cyclic acetal. Draw a reasonable mechanism for the first step of this reaction (NaOH, PhSH, H2O/t-BuoH). RO OR SPh b) According to the article, this transformation proceeds in 63%,7:3 ratio of regioisomers. What are the structures of the two regioisomers? Give a mechanism to explain how the minor isomer is formed.