Structures of four new oxygenated lupanes from Pleurostylia opposita(Celastraceae)

Abstract

Four new oxygenated lupanes isolated from the stem bark of Pleurostylia opposita (Wall) Alston (Celastraceae) have been shown to be lupa-5,20(29)-dien-3-one (2), 6P,20-dihydroxylupan-3-one (5), 3P,6P-dihydroxylup-20(29)ene (6). and GP,28-dihydroxylup-20(29)-en-3-one (8). The structures of these compounds were established on the basis of spectroscopic ( l H n.m.r. and mass spectral) and chemical evidence. Deshielding of three methyl signals in the 'H n.m.r. spectra of 6P-hydroxylupane derivatives has been attributed to 1,3-diaxial interaction between the relevant methyl group and the 6P-hydroxy-group.Pmufiusz-YuA OPPOSITA (Wall) Alston (Celastraceae) is a moderately sized tree found in the dry zone of Sri Lanka. Previous work on the genus PZezcrostyZia has led to the isolation of friedelin , epi-friedelinol, and the spermidine celacinnine from the leaves of P. a f ~i c a n a . ~ Pristimerin, a-amyrin, p-sitosterol, and eight other triterpenes were isolated from the benzene extract of the stem bark of P. opposita. Several lupane derivatives have been isolated from the Cela~traceae.~-' Six of the triterpenes isolated from P. op#osita were found to be lupane derivatives which have not been reported previously in this family. In this paper we report the isolation and structure elucidation of four new oxygenated lupane derivatives. RESULTS AND DISCUSSIONPlant material used in this investigation was collected from Murugandy, in the Jaffna district of the Northern province of Sri Lanka. The benzene extract of the dried, powdered stem bark of a well matured tree of P. opposita yielded pristimerin, a-amyrin, p-sitosterol, and eight compounds (1)-( 8), all of which gave a positive Liebermann-Burchard reaction. Compounds (2), (4), (5), ( 6), (7), and (8) have been identified as lupa-5,20(29)-dien-3-one (2), 20-hydroxylupan-3-onc (4) ,8 6p,20-dihydroxylupan-3-one (5), 3p,Gp-dihydroxylup-20(29)-ene (6), 3pJ20-dihydroxylupane (7) and 6p,28dihydroxylup-20(29)-en-3-one (8), respectively. Compounds (2), (5), (6), and ( 8) are new lupane derivatives. Rigidenol, a lupane derivative with an or-hydroxy-substitutent at C-6 has been reported from Maytenus rigida (Celastraceae) .g Our results indicate this assignment to be doubtful. Hence, ( 5), (6), and (8) are the first examples reported of lupanes with an oxygen substituent at C-6. Di-and tri-oxygenated friedelin derivatives with a 6P-hydroxy-substituent have been reported from Kokoona xeyZanica belonging to the same family.10 l H N.m.r. and mass spectral evidence suggested the presence of a lupane skeleton in (2) and ( 4)-( 8). Two l -H doublets in the 6 4 . 6 4 . 5 region, and a 3-H doublet at 6 1.6-1.7 in the l H n.m.r. spectra of (Z), (6), and (8) indicated the presence of a lup-20(29)-ene system in these three compounds.ll Further, signals due to eight methyl groups, including two singlets at 6 1.1 and 1.2, in the n.m.r. spectra of (4), (5), and (7) showed the presence of a C(Me),OH group, and indicated that these compounds were 20-hydroxylupane derivatives8 Fragments at m / e 21...

Triterpenoid Extractives in the Outer Bark ofBetula lenta(Black Birch)

“…(Lindgren and Svahn 1966;Ekman 1983b) and in B. maximowicziana (Pokhilo et al 1986). It has been found in other species äs well (Dantanarayama et al 1981;Hui and Li 1977).…”

A Novel Secobetulinic Acid 3,4‐Lactone from Viburnum aboricolum

“…The NOESY plot displayed NOE interactions between this H-atom and two Me s at 1.49 and 1.73, the former being larger in magnitude (see Table). The coupling patterns and NOE interactions among these groups allowed the assignment of H a ÀC (6) [5], the downfield-shifted signals for these two Me groups in 1 suggested C(4) to be oxygenated. Its HMBC spectrum (Table) also suggested this connection by displaying the two-bond connections between this C(4) (d 86.7) and the H-atoms of Me(23) and Me(24).…”

“…Bio-assay-guided fractionations traced the activity in the CHCl 3 -soluble fraction. The latter was separated by repetitive column chromatography (silica gel) to yield eight components, including ursolic acid [2], five betulinic acid derivatives, 6b-hydroxy-3,O-didehydrobetulinic acid [3], compound 1, 6a-hydroxy-3,O-didehydrobetulinic acid [3], betulinic acid [4] [5], 6b-hydroxybetulinic acid [6] [7], and two oleanolic acid derivatives, sumaresinolic acid [8] and maslinic acid, the latter being isolated in its diacetate form [9]. Of these, compound 1, a secobetulinic acid 3,4-lactone, was found to be a novel natural product.…”

Cleistanone: A Triterpenoid from Cleistanthus indochinensis with a New Carbon Skeleton

“…This was supported by the downfield proton chemical shifts of CH 3 -25, CH 3 -26, and CH 3 -27 (Table 1) due to 1,3-diaxial interactions between the 6β-hydroxy and the relevant methyl group. [14,15] The spatial interactions of CH 3 -26 (δ H = 1.44 ppm) with CH 3 -27 (δ H = 1.36 ppm) and H-5 (δ H = 1.17) with H-9 (δ H = 1.43) defined the trans-fused junctions for the A/B/C ring systems. Similarly, a trans ring fusion was also assigned to the C/D rings.…”