62(P-43) 面不斉(アレーン)クロム錯体を利用した軸不斉Korupensamine A及びBの全合成(ポスター発表の部)

概要

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Napthyl teterahydroisoquinoline alkaloids, atropisomeric korupensamines A, B and ent-korupensamine B were synthesized by syn-selective cross-coupling of a planar chiral arene chromium complex with naphthylboronic acid, and subsequent axial isomerization or tricarbonylchromium migration to the inverted arene face as a key step. Palladium(0)-catalyzed cross-coupling of planar chiral arene chromium complex 9 with naphthylboronic acid 6 gave syn-biaryl coupling product 10. Syn-biaryl chromium complex 10 was heated in 1:1 mixture of di-n-butyl ether and 1,2-dichloroethane to give a face-inverted anti-biaryl chromium complex 11 without axial isomerization. Korupensamine A was synthesized from the syn-biaryl chromium complex 10 via o-formyl syn-biaryl chromium complex 7, and ent-korupensamine B was prepared from the face-inverted anti-biaryl chromium complex 11. On the other hand, difluoro-substituted syn-biary chromium complex 32 with a formyl group afforded central bond rotated anti-biaryl chromium complex 33 by heating in xylene. The chromium-complexed fluorine atom was easily substituted to an isopropoxy group by nucleophilic substitution. By using these reactions, (+)-2-bromo-3,5-difluorobromobenzaldehyde chromium complex (30) as a single chiral source was converted to atropisomeric korupensamines A and B, respectively.
天然有機化合物討論会の論文
2004-10-01