環状ニトロンに対する求核付加反応を用いる(+)-Casuarineの合成研究　

抄録

Nucleophilic addition of the cyclic nitrone 1 derived from L-xylose with sp, sp2, and sp3-hybridized carbon-nucleophiles was examined. Nucleophilic addition of the lithium acetylide, Li-C≡C-TMS, was found to give the best yield of adduct with excellent stereoselectivity. With this result in hand, concise formal synthesis of (+)-hyacinthacine A2 was achieved by using nucleophilic addition of the nitrone 1 with Li-C≡C-CO₂Et. Next, synthetic study towards (+)-casuarine was made. Nucleophilic addition of the nitrone 2 with Li-C≡C-CH₂OTBDPS afforded the corresponding adduct in high yield. The adduct was converted to the precursor of (+)-casuarine by way of desilylation, half-reduction of the propargyl alcohol moiety by LiAlH₄, reductive cleavage of N-O bond, and dihydroxylation of (E)-double bond of the resulting allyl alcohol.

fig.1