抄録
We reported that the Diels-Alder adduct (2) was transformed into the chiral lactam (4) by regioselective reduction and samarium-induced desulfinylation. Easy availability of the chiral hydroxy-lactam (4) enabled us to exploit stereoselective nucleophilic addition to the acyliminium ion generated in situ from the lactam. We now describe the stereoselective intra- and intermolecular addition to the acyliminium ion derived from the chiral hydroxy-lactam by stereocontrol due to the bicyclo[2.2.1]heptane moiety. [1] Intramoleculer Nucleophilic Addition N-butynyl sulfinylmaleimide (9) was synthesized, and the Diels-Alder adduct (10) was transformed into the chiral lactam (5). The N-butenyl derivative (12), which was obtained by selective hydrogenation of (5), was subjected to N-acyliminocyclization to give the product (13) as the single diastereoisomer. The tetracyclic formate (13) was further converted into (+)-δ-coniceine. Alternatively, (5) was protected as the methyl ether (17), which upon treatment with (PhS)_2 and LDA afforded (18). Exposure of (18) to formic acid produced tetracyclic ester (19) as the single product. Reduction and subsequent flash vacuum pyrolysis afforded the bicyclic amide (21) which was transformed into (+)-trachelanthamidine. [2] Intermolecular Nucleophilic Addition Reaction of (4) with allyltrimethylsilane and with alkylcopper in the presence of a Lewis acid took place in a diastereoselective manner (d.e. 〜100%) to give the product (26). The heptyl derivative (26)(R=heptyl) was converted into (29), which was a precursor in the synthesis of a venom alkaloid analogue (30).
