Buxus sempervirens L. was collected in the Arboretum SAV, Trnava, Slovakia. Previous work on this and sister species is given in refs [2-5]. In the present work a cyclosteroid alkaloid of a novel type 1 has been isolated from the 'strong bases' fraction [6]. This base of molecular formula C27H45NO2 (mp 137°C, diethyl ether; [α]D²⁵ +65°, CHCl3), is the first Buxus alkaloid possessing a tetrahydro-oxazine ring joined to positions 16β, 17α of the androstane skeleton. Its IR spectrum had absorption bands attributable to a C-O-C bond, a cyclopropyl group, a gem-dimethyl grouping and secondary and tertiary amino groups. The PMR spectrum showed signals diagnostic of methylene protons of a cyclopropane ring and further protons indicative of 4 tertiary methyl groups, 1 secondary methyl group, methyls of two methylamino groupings and a -CH2- between two heteroatoms. The MS of this alkaloid exhibited characteristic peaks of a methylamino group at C-3 and a fragmentation pattern substantially different from that of other dibasic Buxus alkaloids, with M⁺ -15 as base peak, thus suggesting some modification of the α-amino-C20-side chain of the pregnane backbone. Biogenetic considerations and the requirement for 6 loci of unsaturation allowed postulation of the structural formula of the base under investigation as being 1. To verify this suggestion the 1 was hydrogenized to afford cyclovirobuxine-C [8] (2) identical in all respects with the authentic specimen. This experiment produced evidence not only the correctness of the proposed structure, but also proof of the stereochemical arrangement of the alkaloid designated buxozine-C. The semisystematic name of this alkaloid of a new type is (4'S)-3',4,4,4',14α-pentamethyl-3β-methylamino-9,19-cyclo-5α-androstano-[16β,17α-e]tetrahydro-1,3-oxazine. Solanum pseudoquina St. Hil was identified by Alfredo Paredes, and a voucher kept at Escuela Politecnica, Quito; trivial name, pululo. This was obtained from the Ecuadorian Andes, on the outskirts of Quito. In previous work, tests have been made for steroidal alkaloids [1]. In the present work green berries of this plant were crushed and extracted with MeOH. Chromatography of the alkaline CHCl3 extract yielded solaquidine (1) as colourless needles, mp 278-281°C. The PMR spectrum showed the presence of two OMe groups, (δ 3.10 and 3.15), a most unusual feature in steroidal Solanum alkaloids. The MS showed a parent peak at m/e 444. Since an elementary analysis indicated the presence of only one N the true MW was established as 445 (C29H51NO3). The base peak at m/e 98 showed the presence of a methyl piperidine side chain, and the two very abundant fragments at m/e 101 (60%) and m/e 127 (32%) indicated that both OMe groups were located at C-3. It has been demonstrated that an ethylene ketal function at C-3 produces mainly fragments at m/e 99 and 125, if rings A and B of a steroid are not substituted. Since solaquidine has two OMe groups at C-3 instead of an ethylene ketal, the fragmentation proceeds in a similar manner, but it produces fragments two a.m.u. greater, m/e 101 instead of 99, and m/e 127 in place of 125. The fact that both OMe groups are attached to the same carbon produces some shielding and explains why these protons appear at higher field than normally expected. The IR of the acetate (2) showed a strong N-