An efficient synthesis of cholanic acids from 20-ketopregnanes

An efficient synthesis of 3β-hydroxy-5-cholanic acid (8) and 3β-hydroxy-Δ⁵-cholanic acid (16) was carried out starting from 5-dihydropregnenolene (1) and pregnenolone (9). The monoacetates (3 and 11), prepared by Grignard reaction of 1 and 9 with 3,3-ethylenedioxypropylmagnesium bromide followed by acetylation, were dehydrated selectively to give the Δ²⁰⁽²²⁾-compounds (4 and 12) which on hydrogenation followed by acid treatment and Jones oxidation yielded 8 and 16, respectively.     

New steroidal sapogenins from the acid hydrolysis product of the whole glycoside mixture of Welsh onion seeds

Two new steroidal sapogenins(1,2) along with five known steroidal sapogenins were isolated from the acid hydrolysis product of the whole glycoside mixture of Welsh onion(Allium fistulosum L.) seeds.Based on comprehensive spectroscopic analyses, including 2D NMR spectroscopy and mass spectrometry,their structures were elucidated as(25R)-19-norspirosta-l,3,5(10)-triene-4 -methyl-2-ol(1),(25R)-spirost-l,4-diene-3-one-2,6-diol(2),(25R)-spirost-l,4-diene-3-one-2-ol(3),(25R)-spirost-4-ene-3-one-2-ol (4),yuccagenin(5),gitogenin(6) and tigogenin(7).     

Synthetic studies in steroidal sapogenins and alkaloids—XII : Synthesis of sceptrumgenin and isonuatigenin

The Michael adduct of 5-nitro-2,2-ethylene-dioxypentan-1-ol acetate with E-5,17(20)-pregnadien-3β-ol-16-one gave on reduction with sodium borohydride and deketalisation, spirost-5-en-3β-ol-25-one. This intermediate was converted to sceptrumgenin through reaction with triphenyl phosphonium methylide and to isonuatigenin by treatment with dimethyl oxosulfonium methylide followed by lithium aluminium hydride.     

A new strategy for synthesizing the steroids with side chains from steroidal sapogenins: synthesis of the aglycone of OSW-1 by using the intact skeleton of diosgenin

The protected aglycone of saponin OSW-1, a new antitumor natural product, was synthesized in 13 linear steps in 9.5% overall yield by utilizing the intact skeleton of diosgenin. This strategy demonstrated a higher efficiency than the routine synthesis of steroids with side chains.     

Revisit to 25R/25S stereochemical analysis of spirostane-type steroidal sapogenins and steroidal saponins via 1H NMR chemical shift data

An approach based on the difference (deltaab = deltaa - deltab) between 1H NMR chemical shifts (deltaa, deltab) of the geminal protons of oxymethylene (H2-26) (delta(ab) = < 0.2 for 25R; delta(ab) = > 0.5 for 25S) is proposed for ascertaining 25R/25S orientation of the 27-methyl group for (22R)-spirostane-type steroidal sapogenins and steroidal saponins. These studies suggested the 25R-orientation of the 27-Me group for the steroidal saponins isolated by Temraz et al. from Tribulus alatus.     

Crabbogenin, 1β-hydroxycrabbogenin,strictagenin and pompeygenin,four new steroidal sapogenins from cordyline stricta leaves

From the leaves of Cordyline stricia Endl. four new steroidal sapogenins crabbogenin {5α-spirost-25(27)-en-3α-ol}, 1β-hydroxycrabbogenin, strictagenin {(20S, 22S, 25S)-5α-furostan-22, 25-epoxy-1β, 3α, 26-triol} and pompeygenin {(25S)-5α-spirostane-1β, 3α-25-triol} have been isolated and their structures determined by chemical and spectroscopic methods.     

First synthesis of steroidal 1,2,4-trioxolanes

Griesbaum ozonolysis of mixtures of methyl 3-(methoxyimino)-5β-cholan-24-oate with ketones (cyclohexanone, methyl trifluoromethyl ketone, and phenyl trifluoromethyl ketone) afforded for the first time steroidal 1,2,4-trioxolanes which were isolated as mixtures of stereoisomers.     

Synthesis of steroidal thiadiazoles from steroidal ketones

Syntheses of steroidal heterocycles containing a five-membered N,S- heterocycle attached at the 6,7 positions of the B ring are reported. 5Alpha-cholestane-6-one (1), its 3beta-acetoxy- (2) and 3beta-chloro- (3) analogues reacted with semicarbazide and aqueous sodium acetate in refluxing ethanol to yield 5alpha-cholestan-6-one-semicarbazone 1a and its 3-beta-acetoxy and 3beta-chloro derivatives 2a and 3a, respectively. The reactions of 1a, 2a and 3a with thionyl chloride in dichloromethane at low temperature afforded the cyclized thiadiazole 4 and its 3beta-acetoxy- and 3beta-chloro analogues 5 and 6 in good yields.     

New synthesis of steroidal tetrahydrooxazin-2-ones

In the DMSO/NaHCO₃ system, 16α-aminomethyl-, 16α-benzylaminomethyl- and substituted benzylaminomethyl-3-methoxy-17β-tosyloxyestra-1,3, 5(10)-triene (3, 5a-k) do not undergo oxidation, but form a tetrahydrooxa-zin-2-one ring (7, 8a-k) via neighboring group participation. Under similar conditions, 16β-aminomethyl-3-methoxy-17β-tosylestra-1,3,5(10)-triene (4) decomposes into 16-methylene-3-methoxyestra-l,3,5(10)-trien-17-one (12).     

Mass spectrometry in structural and stereochemical problems–CXCIV: The mass spectrometric fragmentations of steroidal sapogenins

The characteristic mass spectral fragmentation patterns of the basic structure of the steroidal sapogenin, (25R)-5α-spirostan, have been elucidated through the preparation of analogs with deuterium labels at positions 11, 12, 14, 15, 16, 17, 20, 21, 23, 24, 25, 26 and 27. In addition, the effects of a change of stereochemistry at positions 14 and 20, of the introduction of oxygencontaining functionalities mostly in ring F, and of the incorporation of olefinic unsaturation have been determined through synthesis of many examples.     

25R/25S stereochemistry of spirostane‐type steroidal sapogenins and steroidal saponins via chemical shift of geminal protons of ring‐F

A method based on the differences among the ¹H NMR chemical shifts of geminal protons of ring‐F methylene resonances (H₂‐23, H₂‐24 and H₂‐26) is proposed for ascertaining the 25R/25S stereochemistry of ring‐F unsubstituted spirostane‐type steroidal sapogenins and steroidal saponins. Copyright © 2003 John Wiley & Sons, Ltd.