Ketal, cyclopentylidene diol protection

The 1,3-anti -reduction of (3-hydroxy ketones was utilized in the total synthesis of (+)-roxaticin (14), a pentaene macrolide isolated from streptomycete X-149944 (Scheme 4.2e). The (3-hydroxy ketone 15 underwent 1,3-anti -reduction to afford the diol 16 in 99% yield and greater than 95 5 diastereoselectivity. The resulting diol was then protected as a cyclopentylidene ketal (17) by using cyclopentylidene dimethyl ketal and pyridinium p-toluene sulfonate (PPTS). 

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