抄録
A novel simplified method of the alkylation of alicyclic lithium 1,2-enediolates has been developed by us to create a convenient synthesis of the medium ring sizes (Scheme 1). Based on this method, the total synthesis of diplodialides A(1), C(2), and decan-9-olide (3) was achieved by the following route. 1) Decan-9-olide (3) Bicyclic glycols (8a) and (8b) readily prepared by the alkylation of 1,2-enediolate (7) with 1-iodobutan-3-ol were oxidized to give ten-membered keto lactone (9), which was converted to (±)-decan-9-olide (3) by two steps. 2) Diplodialide C (2) Decan-9-olide (3) was transformed to cis-α,β-unsaturated lactone (12), which upon epoxidation followed by epoxide opening yielded (±)-diplodialide C (2) and epidiplodialide C (14). 3) Diplodialide A (1) Oxidation of (2) and (14) afforded β-keto lactone (15), which in turn was converted to diene lactone (19a) and (19b) by four steps. Hydrolysis of (19a) with trifluoroacetic acid gave (±)-diplodialide A (1) as a sole product. A similar hydrolysis of (19b) produced a mixture of (±)-diplodialide A (1) and cis-diplodialide A (20) in a ratio of 7:5. On the other hand, hydrolysis of (19a) with hydrochloric acid afforded only cis-diplodialide A (20).
