STEREOCHEMISTRY OF HYDROXYLATION REACTIONS ON POLYCYCLIC PYRANS

The configurations at the ring junctions of the tricyclic pyrans 7RS,8 RS)-6,7-dihydroxy-3-oxatricyclo[6.6.0.0(2,7)] tetradec-1-yl acetate, C 15H24O5, and (IRS,2RS,6SR,7SR,8RS)-6,7-dihydroxy-3-ox atricyclo[6.6.0. 0(2,)7]tetradec-1-yl acetate monohydrate, C15H24O5H2O, indicate that, in the reactions leading to these compounds, hydroxylation always take s place on the less hindered side of the substrate, and that the heter ocycle exerts greater steric hindrance than the carbocycle. The struct ures and conformations of the two stereoisomers and their hydrogen bon ding are discussed.