L. Czollner, J. Fröhlich, U. Jordis, B. Küenburg:
"Preparation of 4a,5,9,10,11,12-hexahydro-6H-benzofuro[3a,3,2-ef]benzazepine derivatives";
No. WO 9612692;
A process was developed for producing 4a,5,9,10,11,12-hexahydro-6H-benzofuro[3,2-ef]benzazepine derivs. I (R-R5 = H, halo, HO, alkoxy, alkyl, aryl, aralkyl, acyl, alkylsulfonyl, CHO, etc.; R4R5 may be oxo) in particular the prodn. of galathamine via the novel bromine-N-demethyl galanthamine II (X = H) and the novel bromine galanthamine II (X = Me). Thus, the benzylamine III is oxidatively cyclized into IV. IV is diastereo-selectively reduced by L-selectride to the novel bromine-N-demethyl galathamine II (X = H) without the formation of detectable quantities of epibromine-N-demethyl galanthamine. The novel bromine galanthamine II (X = Me) is obtained by methylation, from which by debromination ()-galanthamine is produced. Pure enantiomers can be demonstrated by pptn. as a salt of a chiral acid (esp. a tartrate). The process gives high yields and pure products at all stages and can thus be conducted on the industrial scale.
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