Steroid alkaloids Apocynaceae

Evidence has been accumulated that the biogenesis of plant steroids proceeds by the same scheme as in animals this sequence was proved up to squalene and recently squalene has been shown to be a precursor of, 8-sitosterol evidence was also adduced that this conversion includes lanosterol as an intermediate (233). Goutarel assumes that the sequence squalene, lanosterol, zymosterol, and desmosterol may be implied also in the biogenetic pathway of Apocynaceae alkaloids (205). It may be assumed that biogenetic intermediates from sterol or triterpene precursors of Apocynaceae or Buxaceae alkaloids, respectively, are 3-and/or 20-ketones which may give rise to mono- and diamines. 

The path from squalene (114) to the corresponding oxide and thence to lanosterol [79-63-0] (126), C qH qO, cholesterol [57-88-5] (127), and cycloartenol [469-38-5] (128) (Fig. 6) has been demonstrated in nonphotosynthetic organisms. It has not yet been demonstrated that there is an obligatory path paralleling the one known for generation of plant sterols despite the obvious stmctural relationships of, for example, cycloartenol (128), C qH qO, to cyclobuxine-D (129), C25H42N2O. The latter, obtained from the leaves of Buxus sempervirens E., has apparentiy found use medicinally for many disorders, from skin and venereal diseases to treatment of malaria and tuberculosis. In addition to cyclobuxine-D [2241-90-9] (129) from the Buxaceae, steroidal alkaloids are also found in the Solanaceae, Apocynaceae, and LiUaceae. 

Steroidal Alkaloids of the Apocynaceae and Buxaceae and Related Compounds , F. Khuong-Huu and R. Goutarel, in Alkaloids , ed. M. F. Grundon, Royal Society of Chemistry, London, 1977, vol. 7, pp. 268-288. 

The stem bark of Holarrhena antidysenterica Wall. (Apocynaceae) yielded the known steroidal alkaloids holarrhimine, isoconessimine, and conimine (108). Leaves of Holarrhena curtisii King et Gamble yielded the known as well as new aminoglycosteroidal alkaloids holacurtine (102) and N-demethylholacurtine (103), respectively (109). 

A number of our regular authors are not participating this year, and I would like to express my appreciation to Drs. Crout and McCorkindale for their contribution to Volumes 6 and 7 and in particular to Drs. Goutarel and Khuong-Huu for reviewing steroidal alkaloids of the Apocynaceae and Buxaceae since the inauguration of this series of Reports in 1971. In this Volume, all steroidal alkaloids are included in Chapter 14. 

The steroidal alkaloids have a nucleus based on 21, 24, or 27 carbon atoms (Fig. 44). The C21 alkaloids are pregnane-derived with nitrogen inserted at C-3, at C-20, or at both positions. They are characteristic of the Apocynaceae Funtumia and Holarrhena species) and the Buxaceae Buxus species). The Buxaceae also produces C24 alkaloids based on the cycloartane skeleton. The most interesting alkaloids are those in the Solanaceae and the Liliaceae. These are C27 alkaloids, and examples include solasodine and solanidine many derivatives are glycosylated. The alkaloids from the Liliaceae, such as veratramine of the white hellebore (Veratrum album), were formerly used for cardiac... 

The genus Malouetia was described in detail, both from the botanical and chemical point of view, by F. Khuong-Huu-Laine et al. (3). The results of extensive investigations of steroid alkaloids of Apocynaceae have been reviewed in several articles (4-8) and in the excellent monograph by Goutarel (9). 

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