By using the known structure and stereochemistry of the alkaloid ormosanine, C20H35N3 (I), as reference, the structure and stereochemistry of the isomeric compounds piptanthine (II), tetrahydro-ormojanine (XIV), isotetrahydro-ormojanine (XIII), and dasycarpine (XX) have been elucidated by isomerization and reduction experiments. Three additional C20H35N3 bases possessing the ormosanine skeleton have been prepared by the reduction of pyridine VII. Thus, of the 15 possible stereoisomers of ormosanine, 7 are now known.The study leads to the stereo-formula XIX for the alkaloid ormojanine, C20H31N3. The alkaloid ormosinine has been found to be a dimer of panamine.Stereochemical aspects of the catalytic and chemical reductions of the double bonds and pyridine rings contained in the described compounds are discussed. A possible biogenetic intermediate is proposed which explains the presence of both antipodal series of Ormosia alkaloids in nature.

A total synthesis of dilactarn (3) possessing the complete pentacyclic skeleton of the Ormosia alkaloids has been completed.Canadian Journal of Chemistry, 47, 509 (1969) The determination of the structure of the Orn~osia alkaloidjarnine by X-ray crystallography (1) led directly to the structure of ormosanine and, through a study of the reduction of the dehydrogenation product (1) (2, 3), to the structure and stereochemistry of additional alkaloids of this type (4). Since the alkaloid piptanthine (2) together with four isomeric bases has already been prepared by a controlled reduction of 1 (4) and since most of the stereochemical and functional variation in compounds of this class occurs in rings A, B, and E, it was deemed desirable to develop a synthetic approach in which ring E would be aromatic to the penultimate stage and in which ring A would be added last. The following total synthesis of the crystalline racemic dilactam (3) satisfies these requirements.The known compound (4) (5), m.p. 126-127", was reduced with Pd-C in ethanol to give an 80 % yield of the oily lactam ester (5), a mixture of at least two isomers.' Treatment of crude 5 with sodium hydride and ethyl acrylate in dimethyl formamide at 110' for 12 h gave the keto-ester (6), m.p. 155-156", in 53% yield. In order to establish its stereochemistry, 6 was hydrolyzed with 10% aqueous sulfuric acid to give 7, m.p. 173-176". Vigorous reduction of 7 with lithium aluminium hydride gave the corresponding hydroxyamine which showed strong Bohlmann bands (6) in the 2800 cm-' region of the i.r. spectrum (CHCI,). Based on previous study (4),'All reported conlpounds showed satisfactory spectral properties, including correct molecular ions in mass spectrometry. For brevity, only spectral data of special significance are given. All crystalline compounds gave correct elemental analysis. Unless otherwise stated, all oily conlpounds were purified by colunln chron~atography on silica gel and were homogeneous in thin-layer chromatography.this clearly establishes that the C,-H is cis to the C,-C, bridge. Treatment of 6 with selenium dioxide and acetic acid in boiling tert-butyl alcohol gave the unsaturated keto-ester (81, m.p.200-201°, in 78 % yield; this was then converted to ketone (9), m.p. 193-194", in 71 % yield on boiling with 10 % aqueous sulfuric acid.Since standard methods applied for construction of ring A using 7, 8, and 9 proved unpromising, the following novel synthetic application of the versatile photo-addition of olefins to a,P-unsaturated ketones2 was developed. Irradiation of 9 in vinyl acetate and tetrahydrofuran (Hanovia 100 W High-Pressure Hg vapor lamp, Pyrex filter) at 25" for 2 h gave a 60 % yield of a mixture composed of four isomers of acetate (10). Bromination of crude 10 with pyridinium bromide perbromide in glacial acetic acid gave a mixture of four bromo-ketones (11) in 78% yield. Treatment of crude 11 with sodium carbonate in aqueous methanol followed by chromatography on silica gel gave a 76% yield of pure keto-aldehyde (12), i.r. max...

A stereoselective synthesis of ormosanine (1), identical in all respects with the naturally occurring racemic alkaloid of O. jamaicensis, has been accomplished. Subsequent transformation of synthetic ormosanine into racemic piptanthine (2) and into d,l-panamine (3) is described. 18-Epiormosanine (22) has also been prepared by total synthesis. Some unusual stereochemical effects allowing the control of configuration at C6, C11, and C18 are discussed.

Degradations of ormosanine, C ? O H~~S~, are described which are in agreement with structure 11 (8) for this alkaloid. Nuclear magnetic resonance study of N-acetyl and AT-~~itroso derivatives has been used to clarify the environment of the secondary nitrogen atoms. Chemical and spectroscopic evidence leads to the forlil~~latioil S V b for the related allialoid orlnojanine,Both alkaloids \\rere found to give 3-?z-pentyl-G,S-dipropyIq~ii1ioline together wit11 the correspondi~i~ 3-72-butyl derivative in a catalytic dehydrogenation. The possible ~nechanism of formation of these deliydrogenation products is discussed and their synthesis is described., .I he presence of a large number of all

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