Author:
Johns SR,Lamberton JA,Sioumis AA,Suares H
Abstract
Catalytic hydrogenation of
schelhammeridine (I) in acetic acid solution gives demethoxydihydroschelhammeridine
(II), 1,2,6α,7- tetrahydroschelhammeridine (III), dihydroschelhammeridine
(IV), and a tetrahydro derivative (V), the formation of which involves cleavage
of the C5-N9 bond. The major product from heating schelhammeridine with 10%
aqueous hydrochloric acid is the alcohol (VIIa) with the configuration at C 3
opposite to that in schelhammeridine. Other products are the alcohol (IX) and
two amino alcohols (Xa) and (XIIa) which have a diphenyl ring system formed by
the aromatization of ring A. The compounds (Xa) and (XIIa) have been shown to
be diastereoisomers with the same absolute configuration for the dissymmetric
diphenyl system, but the opposite configuration at C 7, and they have been
characterized as N-acetyl derivatives (Xb) and (XIIb) which have been assigned
the respective configurations shown in (XX) and (XVIII). On heating with acetic
anhydride, schelhammeridine is converted into the N,O-diacetyl compound (XVa)
which on hydrolysis affords (XVb), the optical antipode of (Xb). All three
stereo-isomeric N-acetylamides (Xb), (XIIb), and (XVb), are oxidized to the
same optically inactive ketone (XI). A mechanism for the acetic anhydride
reaction that explains the formation of only a single isomer is discussed, and
it has been shown that the formation of (XVa), enantiomeric with (Xc), in this
reaction necessarily involves inversion of the configuration of the diphenyl
system in the first-formed product, which must be the O-acetyl derivative of
(XVIII). It is concluded that amide alcohols (XVIII) and (XX) retain the
configuration for the diphenyl system that would be predicted from the known
absolute configuration of schelhammeridine, but that the initially formed O-acetyl
derivative of (XVIII) obtained in the reaction with acetic anhydride is
converted quantitatively at the temperature of the reaction mixture into the O-acetyl
derivative of (XXI) by inversion of the diphenyl configuration.
Cited by
24 articles.
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