Absolute configuration of
d-thalictricavine (I),
d-corydaline (II),
d-corybulbine (III), and
d-isocorybulbine (IV) was determined. III and IV are derived to II by methylation with diazomethane. Dehydrogenation of I with mercury (II) acetate gives 13-methyl-2, 3-methylenedioxy-9, 10-dimethoxy-5, 6-dihydrodibenzo[
a,
g]quinolizinium derivative (VI), whose reduction with sodium borohydride or zinc dust and acetic acid affords
dl-thalictricavine (VII). Similarly, treatment of II with mercury (II) acetate gives a dehydro base (VIII) whose reduction affords
dl-corydaline (IX). Infrared spectra of I and VII, and of II and IX, in chloroform solution are identical, showing absorption of
trans-quinolizidine at around 2760cm
-1. From the result of these oxidation and reduction reactions, the methyl group in 13-position of I and II is known to take a stable configuration was further confirmed by the comparison of NMR with that of 1-methylquinolizidine and its salt. NMR spectra of I and II in chloroform show a doublet at δ
Me=0.93-0.94 p. p. m., and their acetate at δ
Me=0.97-0.98 p. p. m. This agrees with the observation on 1(e)-methylquinolizidine. I and II also show a positive Cotton curve in ORD. Based on these experimental evidences, absolute configuration of I, II, III, and IV was determined as 14(
R)-13(
S, e).
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