Tetranortriterpenoids and related compounds. Part 25. Two 3,4-secotirucallane derivatives and 2′-hydroxyrohitukin from the bark of Guareacedrata (Meliaceae)

Abstract

24-trien-3,21-doc acid 1, the corresponding 3-monomethyl ester 12, and 2'-hydroxyrohitukin 13, have been isolated from the bark of Glrcrrecl cedrcttrr (Meliaceae). The structuresof 1 and 12 were confirmed by correlation with methyl 3-oxotirucalla-8.24-dien-21-oate (methyl isoelemonate) 6. The 'Hand I'C nmr data are reported.On a isole, de I'ecorce de Glrrrrrcl ceclrrrtcl (Meliaceae), trois triterpenoides nouveaux, I'acide 3,4-secotirucalla-4(28).7,24-tritn-3,21-dioique 1, son ester rnethylique 12 et 2'-hydroxyrohitukin 13. On a confirrne les structures 1 et 12 par une correlation avec methyl 3-oxotirucalla-8.24-dien-21-oate 6. Les spectres rmn sont presentks.In a continuation of our investigation (1,2) of the conditions the dimethyl ester 2 gave the chloroconstituents of the Meliaceae family we have diene 5 70.8 (s, C-25), 147.3, 137.6 (both s, C-8 examined the extract of the bark of G~iarea cedrata and C-9), 129.8 (s, C-4), 1 13.8 (t, C-28)). This and have isolated three new compounds, the ring A acid-induced isomerisation of a hindered trisubstisecotirucallane derivatives A 1 and B 12 and 2'-tuted to a tetrasubstituted double bond is reminishydroxyrohitukin 13, whose structures were as-cent of the behaviour of A7 tetracyclic triterpensigned on the following evidence.oids, e.g. odoratol (3), and, taken in conjunction Compound A 1, C3,H4,04, has spectroscopic with the above spectroscopic evidence, led us to 1 properties consistent with the presence of two car-as a biogenetically acceptable structure for comboxyl groups (ir: 3200-2500 (br), 1709 cm-1; 6c pound A. This was confirmed in the following way. 183.5 and 181.3), an exomethylene ( 6~ 4.80 (2H, Methyl 3-oxotirucalla-8,24-dien-21-oate 6, isobs); 6 c 132.4 (s) and 114.1 (t)), and two trisub-lated from elemi resin according to the procedure of stituted double bonds (tjH5.23 (m, H-7) and 5.09 (bt, Halsall and co-workers (4). was hydrogenated over H-24); 6,. 123.5 (d, C-24), 147.5 (s, C-25), and 1 18.0 palladium/charcoal to give the non-crystalline (d, C-7), 145.8 (s, C-8)). The molecule is therefore 24,25-dihydro-derivative 7. Baeyer-Villiger oxidatricarbocyclic. In addition there are three tertiary tion of 7 with peracetic acid afforded a mixture of methyls (6H 0.81, 0.87, and 0.95) and three vinyl the lactone 8 and the epoxylactone 9, separable by methyls ( 6~ 1.55, 1.65, and 1.75). Hydrogenation preparative tlc. The former was converted into the over palladium/charcoal of the dimethyl ester 2, diene dimethyl ester 11, via the hydroxy dimethyl obtained by reaction of 1 with diazomethane, af-ester 10, by alkaline hydrolysis, methylation, and forded the tetrahydroderivative 3 whose I3C nmr dehydration with thionyl chloride. Hydrogenation spectrum (6c 118.3 (d, C-7) and 145.6 (s, C-8)) of 11 yielded dimethyl 3,4-secotirucall-8-enclearly showed that one of the trisubstituted double 3,21-dioate 4, identical in all respects with the bonds was resistant to hydrogenation under normal product of acid isomerisation of dimethyl tetraconditions. On treatment with dry hy...

Tirucallane triterpenes from the leaf extract of Entandrophragma angolense

“…Ring A-seco protolimonoids structurally similar to compounds 2 and 3, are entandrolide, isolated from the seeds of E. angolense (Okorie and Taylor, 1977) and the carboxylic acids 4 and 5 from the bark extract of Guarea cedrata (Akinniyi et al, 1980). The 13 C NMR frequencies reported for them are consistent with our assignments.…”

Complete assignments of 1H and 13C NMR data for rings A,B‐seco limonoids from the seed of Aphanamixis polystachya

“…34 The only difference between 4 and 11 is similar to the difference between 3 and 9. 1 H-1 H COSY and HMBC spectra in 4 exhibited the presence of a 2-hydroxy-3-methylpentanoate group, which was replaced by 3-methylbutanoate moiety in 11.…”

Mayombensin, a New Azadirachtin I Derivative with Unusual Structure from Guarea mayombensis

“…Its IR spectrum exhibited typical absorptions for hydroxy (3423 cm − 1 ), ester carbonyl (1697 cm − 1 ), ether (1268, 1142, 1075 cm − 1 ), and double bond (1652 cm − 1 ) functionalities. The UV spectrum showed a peak at 220 nm due to the π-π * transition of an α,β-unsaturated carbonyl group [8,11]. The 13 C NMR spectrum of 1 provided evidence for a conjugated ester carbonyl group by signals at δ C = 167.6 (C-1') and of two olefinic carbon atoms at δ C = 137.8 (C-3') and 130.1 (C-2').…”

“…A few pharmacological studies demonstrated anti-inflammatory, antiviral, and antiprotozoal activities of some Guarea extracts [3][4][5][6]. Previous phytochemical investigations on this genus led to the isolation and identification of a wide variety of constituents including sesqui-, di-, and triterpenes, limonoids, steroids, flavonoids, and coumarins [3,[7][8][9][10]. Although a high number of chemical studies on the genus Guarea have been reported, none is known on Guarea mayombensis Pellegr., which is a big tree up to 10-15 m high, commonly distributed in tropical Africa.…”