Structures of three C32 triterpenoids from Neolitsea pulchella

Abstract

Three triterpenoids isolated from Neolitseapulchella, have been proved by n.m.r. and mass spectral data, and chemical correlations with one another and with cycloneolitsin (3p-methoxy-24,24-dimethyl-9,19-cyclolanost-25-ene) to be 3~-methoxy-24,24-dimethyl-lanosta-9(11).25-diene (I), 24,24-dimethyl-lanosta-9(11),25-dien-3-one (11), and 24chydroxy-3 pmet hoxy-24,2 5d i met h y I -1 a no st -9 ( 1 1 )e n e ( 111).THE isolation of compound (I) C33H& from Neolitsea pulcheZla was first reported in 1967 when it was indicated by spectroscopic evidence to be the methyl ether of a tetracyclic triterpene alcohol, C3,H5,0, which contained two double bonds. It was later discovered that chromatography of the light petroleum extract of the stems of the same plant yielded besides (I) in the earlier fractions, a second compound C3,H5,0 (11), m.p. 168-171", [a], +61.0°, followed by a third compound C33H5802The n.m.r. spectra of both (I) and (11) indicate the presence of an isopropenyl group [S 4.68 (ZH, m) and 1.68 p.p.m. (3H, s)], and those of all the three compounds a trisubstituted double bond [8 5-23 (lH, m)]. Both (I) and (111) were shown to contain an equatorial methoxy-group2 [a 3.36 (3H, s) and 2-57-2-76 p.p.m. (IH, ca. q)], and (111) a tertiary hydroxy-function [6 1-36 (lH, s, exchangeable) and no multiplet signal at 8 3-0-4.0 p.p.m.1. (111), m.p. 272-275", [a]= +52.0". Each of the three compounds gave a positive Liebermann-Burchardt reaction.The i.r. spectra of all three compounds indicate the presence of a trisubstituted double bond (vmz 3050, 862, 814 cm-l), those of (I) and (11) a vinylidene group (3090, 1640, 890 cm-l), and that of (111) an equatorial ether linkage (1100 cm-l) t [similar to that of (I)], and a tertiary hydroxy-group (3625 cm-1). The presence of a carbonyl group in a six-membered ring in (11) is revealed by an absorption at 1710 cm-l. Taken in CS,. The value 1090 cm-1 in ref. 1 should be 1100 crn-l.Ritchie et aL3 recently isolated from Neolitsea dealbata a new triterpene cycloneolitsin, C,H5,0, and established its structure as 3~-rnethoxy-24,24-dimethyl-9,19-cyclolanost-25-ene (IV). Since compounds (1)-(111) were obtained from a species of the same genus, it was probable that they were closely related to (IV), since all of these compounds were unusual CS2 triterpenoids. The remarkable difference is that (IV) contains a cyclopro-

Triterpenoids from the Orchid Eria acervata

“…Similarly, the essentially identical oc values of the above carbon atoms of 2c, 2f4. 2g 12 and 2h 13 confirmed the identical structure of the carbocyclic part and the acyclic side chain containing C-20 and C-21 of all the four compounds having a keto group at C-3 and a 9 .11-double bond in a lanostane basic skeletal structure. The placement of the trisubstituted double bond between C-7 and C-8 in 2c and hence in 2a was ruled out by the fact that this would have led to a considerable downfield shift of the olefinic methine carbon [ca.…”

“…The assignments of the chemical shifts of most of the carbon atoms of the C-17 side chain as well as those of the carbocyclic part of 2a were finally confirmed by 1-bond (HMQC) and 2-and 3-bond (HMBC) 1 H- 13 C correlation spectral analysis. The assignments of the corresponding carbon resonances of 2b and 2c were also affirmed by analogy with those of 2a.…”

Structures of three new 24,24‐dimethyl‐Δ7‐sterols fromGynostemma pentaphyllumfromGynostemma pentaphyllum

“…The structures of these sterols are unusual in the sense that these contain an acyclic, quaternary carbon in the side chain. Although several sterols from some marine sponges (6,9,10) and triterpenoids including 2c-methyl ether from Neolitsea species (Lauraceae) (5,11) are already known to possess side chains with the quaternary center at C-24, this study seems to be the first demonstration of the…”

Chemical constituents of plants from the genus Neolitsea

“…Chan and Hui isolated three C 32 triterpenes 71-73 by column chromatography of the light petroleum extract [23]. In addition, analysis of a larger quantity of a similar extract led to the discovery of three related minor triterpenes 74-76 [22,23]. Compound 77, a new cycloartane, was reported from N. sericea in 1993, and further investigation of this plant revealed three new lanostanes 78-80, along with a known compound 81 [24,43].…”