The stereochemistry of intermediates involved in the synthesis of tricyclovetivane sesquiterpenes

The stereospecificity of addition to the double bond of 2-substituted bicyclo6.2.1.0^1·6]undec - 5 - enes has been studied and shown to be influenced mainly by the bicycloheptyl moiety in the case of epoxidation and hydroboration. These reactions proceed to give predominantly products of endo attack on the double bond. However for osmylation the important effect is the stereochemistry of the C₂-substituent due to steric interactions involved in the cyclic osmate ester intermediate. This results in attack by OsO₄ on the double bond trans to the C₂-substituent.