Synthesis of lucidones

Abstract

Reaction of 2-cinnamoyl-3-hydroxy-5-methoxy-1,4-benzoquinone (10) with acetic anhydride-dimethyl sulphoxide yielded (E)-4-(cinnamoylmethylene)-2-methoxybut-2-en-4-olide (4). Assignment of configuration of the exocyclic double bond in (4) is based on comparison of ¹H n.m.r. shift data and ³J(C-3,5-H) value with those of 4-ylidenebutenolides (11)–(13).

In the presence of sodium methoxide, (4) undergoes ready rearrangement affording lucidone (1a) and hence methyl-lucidone (1b).