Alkaloids, Buxus

Buxus alkaloids based on 19-nor-B-homopregna-9a(10), 9(11)-diene have been reviewed (W. Turowska-Jones and U. Wrzeciono, Chetn. Abs., 1976, 35, 21695). Recent work on Bilxus bases generally has also Teen reviewed [J. Tomko and Z. Voticky, lUPAC Int. Symp. chetti. nat. Prod., 1978, 4, Part 1, 260). 

Amongst newly-isolated Buxus bases are A/3-acetyl cycloprotobuxine C (30) from B. sempervirens (S. Y. Yunusov, Khim. prirod. Soed., 1975, 176), buxaminol B (31) and cyclobullatine A (32), the last two both from B. sempervirens var. butlata Kirchn.(Voticky et al.. Coll. Czech, chem. Comm., 1975, 40, 3055). The structures are based on spectroscopic properties and correlations with known bases. 

The a-configuration for the 3-methyl ami no group follows from a comparison of hydrolysis rates of 3-iV-acyl compounds (Yunusov, et aZ.,Chem. Abs., 1975, 128654 1977, 86, 

That cyclobuxamine H (34) has a 4a-methyl group is confirmed by a demonstration that in a Ruschig degradation epimeriza-tion of a 43-methyl group may occur simultaneously (Voticky and V. Paulik, Coll. Czech, chem. Comm., 1977, 541). 

Buxozine C is a new alkaloid of B. sempervirens it is formulated as the novel structure (38) largely on spectral evidence, but also because it suffers hydrogenolysis to the known cyclovirobuxine C (39) (Voticky et al., Coll. Czech, chem. Comm., 1977, 4, 2549 Phytochem., 1977, 

Recent work on the Buxus alkaloids has been reviewed.6 Cyclobuxines B and D, cycloprotobuxine D, cyclovirobuxine D, and two new alkaloids have been isolated from B. sempervirens. It was suggested that one of the new bases possessed the structure TV-benzoyl-cycloprotobuxine C (6).7 

The distribution of cycloprotobuxine D (13a) in various parts of Buxus microphylla has been described. The same species has yielded also cycloprotobuxine C (13b), cyclovirobuxine C (13c), 

The Solanurn steroidal alkaloids have been the subject of an excellent and comprehensive review which contains also some material relevant to Section 4. 

A single-crystal X-ray diffraction study has shown that sola-maladine possesses the pyrroline structure (14) rather than the 

It was reported earlier that 16g-hydroxy-22,26-epiminocholestane derivatives such as solaverbascine (16) were oxidised smoothly by manganese dioxide to yield spirosolane derivatives such as sola- 

Khodzhaev, R. Shakirov, and S. Yu. Yunusov, Khim. prirod. Soedinenii, 1975, 176. 

Voticky, O. Bauerova, and V. Paulik, Coll. Czech. Chem. Comm., 1975, 40, 3055. 

With thionyl chloride (108a) gave (108b) which was transformed to (108c) and (105b) by hydrogenolysis in the presence of palladium charcoal in alkaline medium. 

Acetylation and reduction with sodium borohydride of (106a) led to (109) dehydrated to (110). Lithium aluminium hydride reduction of the oxiran ring of (110) afforded the tertiary alcohol (111) identical to N-isobutyrylbuxaline F, isolated from Buxus balearica whereby structure and stereochemistry were established. 

With p-nitroperbenzoic acid (112) led to (113), reduced with lithium aluminium hydride to (114). Oxidation of (114) afforded the lactone (115), so demonstrating the la-lOa stereochemistry of the oxiran ring of (113). 

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Buxus alkaloids have a imique steroid-triterpenoid pregnane type skeleton with C-4 methyls, 9fl, lOp cycloartenol system with a degraded C-20 side chain [21-33]. These alkaloids exhibit varions biological activities including anti-HIV, anti-TB,... 

Corded, G.A., 1981, Buxus, Alkaloids A Biogenetic Approach. In Introduction to AlkaloidsNiXey Interscience, New York, pp 907-925. 

Partial syntheses of mangiferolic acid (67), buxandonine (68) and cycloprotobuxines A (69) and F (70)" from cycloartenol, and ambolic acid (71) from cyclolaudenol have been reported. Papers on the Buxus alkaloids include contri-... 

The Buxus alkaloids, as the nitrogenous compounds isolated from this family are commonly known, have been recorded from 33 species. The genus Simmondsia has been placed in a family of its own, Simmondsiaccac its seeds have been reported to give a positive alkaloid test but other than a cyanoglycoside, no alkaloid has been isolated. 

The intramolecular hydrogen exchange that occurs during fragmentation of 3-dimethylamino-steroids in the mass spectrometer has been studied.9 The chemistry of uiose Buxus alkaloids which are based on the 19-nor-B-homopregna-9a(10),9(ll)-diene nucleus has been reviewed.10... 

The full paper on the synthesis of pollinastanol from cycloartanol has been published.21 The revision of stereochemistry at C-4 in the Buxus alkaloids, suggested by 13C chemical shift considerations,22 has been confirmed by X-ray analysis of the derivative (18) of cyclobuxidine F.23 Assignments of the 13C resonances of a series of cycloartanes have been reported.24... 

Buxozine-C (22) was isolated from Buxus sempervirens It is the first buxus alkaloid having a tetrahydrooxazine heterocycle fused in positions 16 , lip of the steroid backbone. 

Noteworthy is the isolation of irehine, initially named buxomegine, from the leaves of Buxus sempervirens (51, 52). This finding is of interest from the biogenetic point of view since this is the only case where a simple pregnane derivative was found among Buxus alkaloids. 

Depending on the nature of the skeleton and substitution in positions 4 and 14, the Buxus alkaloids containing 2 atoms of nitrogen can be divided into several groups which are represented by formulas CCLXII-CCLXXI and designated by the respective trivial names. The several mononitrogen alkaloids isolated to date correspond in their substitution pattern at C-4 and C-14 with the above dibases. 

As concerns the isolation of Buxus alkaloids, this was conducted by extraction of the plant material with a suitable organic solvent directly (id) or after previous treatment with acetic acid (52, 180, 187) or after basification with ammonia or soda (188). The total alkaloids were often fractionated into weak and strong basic portions by extraction from aqueous solutions of alkaloid salts at appropriate pH and then subjected to separation by means of adsorption or partition chromatography (189). 

The above mentioned isomerization of CCCLI to CCCLII constitutes a route from the 9/3,19-cyclosteroids to a new skeletal type which is characteristic of a small group of Buxus alkaloids and will be dealt with in the subsequent text. Another reaction applied to an analogous structural type and leading to cleavage of the cyclopropane ring was reported by Kupchan and Abushanab 219) who had subjected 9, 19-cyclo-5a-pregnane-3,l 1,20-trione-3,2()-diethylene ketal to Wolff-Kishner reduction and obtained a mixture of 10-epimeric ketals CCCLX and CCCLXI. 

No attempt as yet has been made to study the biogenesis of Buxus alkaloids. Indirect evidence gave rise to the presumption that in the biogenetic scheme lanosterol is followed by cycloartenol (or similar triterpene type). Goutarel (205) tentatively proposed a possible pathway via lanosterol, cycloartenol, 9j8,19-cyclo-4,4, 14a-trimethyI-5a-pregnan-3(8 - ol - 20 - one, 9, 19 - cyclo - 4,4, 14a - trimethyl - 5a - pregnan - 3,20 - dione, mono-, and diaminosteroids. 

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