A large number of biologically important natural products are derivatives of asymmetric g - and d - lactones. In addition, these ubiquitous compounds, are valuable synthetic key intermediates. For example, d -lactones of the general formula 5 or 6 , are starting materials for the synthesis of LTB5, malyngolide, milbemycins, spongistatins and the mevinic acid family of cholesterol-lowering agents, while g -lactones, 3 or 4, are synthetic precursors of disparlure, whisky and cognac lactones and nephrosteranic acid. Literature abounds of synthetic schemes for the construction of specific members of this class of compounds. Sugars, chiral auxiliaries as well as Sharpless’ asymmetric epoxidation and dihydroxylation processes have been employed in many ways for their preparation. However, most of them luck generality and/or versatility.

Our strategy towards the synthesis of the title compounds is depicted above. Accordingly, the commercially available parent lactones are coupled under stereocontrolled conditions (using the Wittig-Schlosser protocol) to afford the entire carbon skeleton. Subsequent oxidation and Sharpless’ asymmetric dihydroxylation provides the desired stereochemistry of the resulting diol. Finally, direct lactonization or a SN2 induced cyclization affords the final products. Thus, (- )-muricatacin is synthesized in six steps (43 % overall yield). Furthermore, (5R, 6S)-6-acetoxy-hexadecanolide is prepared in eight steps (38 % overall yield) via a carbonate ester, utilizing a novel lactonization with inversion of stereochemistry.