40 α置換β-ビニルブテノリドによるアヌレーション反応 : フロベンタレンおよびパニクリドAの合成研究

概要

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α-Methyl-(2) and α-phenylthio-β-vinylbutenolides (3) have been developed as new lactone annulation reagents. These reagents were prepared as shown in Scheme 1 and 2. Carbanions of 1,3-di-carbonyls or of α-cyanoketones conjugatively added to these reagents and the adducts underwent aldol-like cyclization under reaction conditions to give annulation products, some of which were recgnized as useful synthetic intermediates for natural lactones and furans. The former butenolide 2 reacted with methyl 2-formyl-6-methyl-5-heptenoate (11) to yield a mixture of annulation products 12a and 12b, which were converted into furoventalene (4), respectively (Scheme 1 and 2). Reaction of some β-diones and α-cyanoketones with the latter butenolide (3) resulted in formation of annulated products in good yields (Table 1). The annulation products were dehydrated and then oxidized to lead to sulfoxides, which on treatment with acetic an-hydride and pyridine, afforded rearranged products (Table 2). The rearranged product 25a was transformed into hydroxylactone 30 (Scheme 4). As an application of these reactions, the total synthesis of paniculide A (5) has been attempted starting with the rearranged product 27 (Scheme 5 and 6).
天然有機化合物討論会の論文
1981-09-10