Lanostane

Triterpenoids are a major group of natural products in higher plants. The tetracyclic triterpenoids, based on the lanostane, euphane, onocer-ane, and dammarane skeletons, are found mostly in vascular plants and... 

The transformation of the lanostane keto-epoxide (72) into the cucurbitacin derivative (73) has been achieved with boron trifluoride in acetic anhydride. The presence of the acetic anhydride appears to favour the backbone rearrangement. The structure of (73) was confirmed by correlation with the oxidation product (74) of deoxybryogenin acetate. Two new cucurbitacin glycosides, arvenins 1 (75) and II (76) from Anagallis arvensis, have been reported. ... 

Fig. (6). Structures of squamocin from Uvaria pauci-ovulata and lanostanes from Neolitsea sericea...

Three lanostane carboxylic acids, 16a-hydroxydehydrotrametenoIic acid (49) [60], 16a-hydroxytrametenolic acid (50) [60], and... 

Fig. (7) A and shows the time dependence of skin tumor formation in the groups treated with DMBA/TPA, with or without 0.2 pM each of three lanostanes, pachymic acid (59), 16a-hydroxytrametenolic acid 3-0-acetate (51), and poricoic acid B (64) [54]. The first tumor appeared at week 11 in the group treated with DMBA/TPA. In the groups treated with DMBA/TPA and 59, 51, and 64, the first tumor appeared at week 13, 14, and 13, respectively. The percentage of tumor-bearing mice treated with DMBA/TPA was 73% at week 20, whereas the percentages in the groups...

Bark four 17,14-friedolanostanes and five lanostanes, as well as friedelin (Vieira etal., 2004). 

The distribution of lanostane triterpenoids in wood-rotting fungi, mainly of the Polyporaceae and related families, has been reviewed.17 A series of related compounds, senexdiolic acid (12), senexonol (13), senexdione (14), and oxidosenexone... 

Whereas empirical force-field calculations predict a ring A boat conformation for lanost-8-en-3-one, combined empirical force-field-extended Hiickel molecular orbital calculations favour a ring A chair conformation. Europium-shift n.m.r. results indicate that the molecule adopts the latter conformation. Studies on the peracetic acid-boron trifluoride etherate Baeyer-Villiger oxidation of 4,4-dimethyl-3-keto-triterpenoids to 5-lactones (18) and their subsequent ring contraction to y-lactones have been reported. Dehydrogenation of lanost-8-en-3j8-ol with 2,3-dichloro-5,6-dicyanobenzoquinone afforded, in addition to the corresponding 7,9(1 l)-diene, the aromatic seco-lanostane derivatives (19)... 

Lanost-8-en-3-one 9, as well as methyl oleanonate, afforded regioselectively the corresponding [2,3-first synthesis of a new lanostane triterpenoid 11 with a cyano enone moiety in ring A, interesting from the perspective of biological activity, was also achieved <03JOC4991>. 

C a 7) ketones [28]., and in the cleavage of ring A of lanostan-g-one [31]. In each case the initial bond cleavage gave the expected more stable of the possible alkyl radicals. 

In the lanostane series, Lewis acids converted the 8a,9a-epoxide (422) into the 7,9(1 l)-diene (423), and the 9a, 1 la-epoxide (424) into a mixture of the 9)3,11-ketone (425) and the diene (426), resulting from a partial backbone rearrangement of a C(9)-carbonium ion. Although 9a,lla-epoxyandrost-4-ene-3,17-dione reacted with boron trifluoride to give only a modest yield of a 19(10— 9)aheo... 

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