Synthetic Studies on Lythraceae Alkaloids via [3+2] Cycloaddition. I. Total Synthesis of Some Simple Phenylquinolizidine Alkaloids and Ester Alkaloids

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A general synthetic route to Lythraceae alkaloids based on a regio- and stereoselective [3+2] cycloaddition reaction has been developed. The [3+2] cycloaddition of the nitrone 5 with the olefins 14 and 26 gave the adducts 15 and 27 which, upon treatment with methanesulfonyl chloride followed by reductive cleavage of the N-O bonds and acetylation, gave the trans-quinolizidines 18 and 30 and the cis-isomers 20 and 32 in reasonable yields. The cis-isomers were converted into the simple phenylquinolizidine alkaloid, (±)-2,and the ester alkaloid, (±)-10-epi-desmethoxyabresoline (4). On the other hand, (±)-1,(±)-lasubine II (23), and (±)-abresoline (3) were synthesized efficiently from the trans-isomers, after inversion of the configuration at the C-2 position by means of the Mitsunobu reaction.
社団法人日本薬学会の論文
1984-10-25