Synthesis of 14β-cholesta-5,7-dien-3β-ol

5, 7-Cholestadien-3β-ol was transformed into 14β-cholesta-5, 7-dien- 3β-ol in six steps. The inversion of the stereochemistry at C-14 was obtained by a selective protection of the Δ⁵ and the elaboration of the Δ⁷ double bond.     

A novel olefinic rearrangement. The enzymic conversion of cholesta-7,9-dien-3β-ol into cholesta-8,14-dien-3β-ol

1. [3alpha-(3)H]Cholesta-7,9-dien-3beta-ol is converted in high yield into cholesterol by a 10000g(av.) supernatant fraction of rat liver homogenate. 2. Incubation of cholesta-7,9-dien-3beta-ol with [4-(3)H]NADPH and rat liver microsomal fractions under anaerobic conditions resulted in (3)H being incorporated into the 14alpha-position of cholest-7-en-3beta-ol. 3. Under anaerobic conditions in the absence of NADPH cholesta-7,9-dien-3beta-ol was isomerized into cholesta-8,14-dien-3beta-ol by rat liver microsomal fractions.     

Mode of formation of cholesta-5,7-dien-3β-ol from cholest-5-en-3β-ol by larvae of Calliphora erythrocephala

1. The conversion of cholest-5-en-3beta-ol (cholesterol) into cholesta-5,7-dien-3beta-ol by axenic Calliphora erythrocephala larvae was demonstrated. 2. The transformation is probably direct (Delta(5)-->Delta(5,7)) and does not involve a Delta(0) intermediate (Delta(5)-->Delta(0)-->Delta(7)--> Delta(5,7)). 3. Delta(7)-bond formation involves the stereospecific elimination of the 7beta hydrogen atom. 4. The relative amounts of free and esterified sterols were determined in larvae grown on cholesterol as sole sterol source and on 5alpha-cholestan-3beta-ol supplemented with minimal amounts of cholesterol. 5. The significance of the results is assessed in relation to the probable role of cholesta-5,7-dien-3beta-ol as an intermediate in the biosynthesis of ecdysones.     

5α-cholesta-7,24-dien-3β-ol as a major sterol of the male hamster reproductive tract

Marked variations in the 3β-hydroxysterol content of hamster spermatozoa were observed as they progress through the epididymis. Cholesterol is the major sterol of caputal spermatozoa while the concentration of precursors of cholesterol was higher than that of cholesterol in caudal spermatozoa. One of these precursors has been identified as desmosterol. A second sterol has now been identified as 5α-cholesta-7, 24-dien-3β-ol by GLC-MS and by NMR. Its concentration is approximately 3-fold higher than that of cholesterol. This 3β-hydroxysterol is also found in epididymal tissue.     

The transformation of 10α-cucurbita-5,24-dien-3β-ol into cucurbitacin C by seedlings of Cucumis sativus

Labelled 10α-cucurbita-5,24-dien-3β-ol, the simplest tetracyclic triterpene with a cucurbitane skeleton, was transformed into cucurbitacin C in Cucumis sativus seedlings. This transformation has been previously postulated, but this is the first time it has been demonstrated to operate in plant tissues. Two other potential precursors of cucurbitacins, cycloartenol and parkeol, were incubated under the same conditions. Cycloartenol gave only the expected phytosterols whereas parkeol was recovered unchanged.     

Cyclization of squalene-2,3-epoxide to 10α-cucurbita-5,24-dien-3β-ol by microsomes from Cucurbita maxima seedlings

Labelled 10α-cucurbita-5,24-dien-3β-ol was obtained from [3-³H]squalene-2,3-epoxide incubated with microsomes of Cucurbita maxima seedlings. By contrast the lanostane triterpenoids [2-³H]cycloartenol, [2-³H]parkeol and their corresponding derivatives [2,12-³H]11-ketocycloartenol and [2-³H]24,25-dihydro-90α,11a-epoxyparkeol, incubated under the same conditions, gave no rearranged products with a cucurbitane skeleton. These results suggest that biosynthesis of cucurbitane triterpenoids from squalene-2,3-epoxide occurs through direct cyclization without the intermediacy of lanostane-type triterpenoids such as cycloartenol or parkeol. Labelled cycloartenol, α-amyrin, β-amyrin and 24-methylenecycloartanol were also obtained from [3-³H]squalene-2,3-epoxide in the same enzymatic system yielding labelled 10α-cucurbitadienol.     

24β-Ethyl-31-norlanosta-8,25(27)-dien-3β-ol and 24β-ethyl-25(27)-dehydrolophenol in seeds of three cucurbitaceae species

The structures of two 4α-methylsterols is isolated from Cucumis sativus(Cucurbitaceae) seeds were determined based mainly on their ¹³CNMR spectra as 24β-ethyl-31-norlanosta-8,25(27)-dien-3β-ol and 24β-ethyl-25(27)- dehydrolophenol, respectively, of which the former is a new sterol from natural sources. These two 4α-methylsterols were identified in the seeds of two other Cucurbitaceae species, Lagenaria leucantha var. Gourda and Citrullus battich. The probable biogenetic significance of the two 4α-methylsterols is discussed. Other 4α-methylsterols identified in the seeds of the three Cucurbitaceae species were obtusifoliol, cycloeucalenol and gramisterol.     

14α-methyl-5α-ergosta-9(11)24(28)-dien-3β-ol a sterol from Gynostemma pentaphyllum

A new sterol isolated from the aerial parts ofGynostemma pentaphyllum has been shown to be 14α-methyl-5α-ergosta-9(11),24(28)-dien-3β-ol.     

Biotransformation of 5-en-3β-ol steroids by Mucor circinelloides lusitanicus

In this work, we report the mode of biotransformation of 5-en-3β-ol steroids using Mucor circinelloides lusitanicus for the first time. Here, we selected seven 5-en-3β-ol steroids as substrates. The main characteristic of the fungus was to introduce a 7α-hydroxyl group into substrates 1--5. With substrate 2, 3β, 7α, 11α-trihydroxypregna-5-en-20-one (2b) was obtained as the final product in good yield (46.4%). All the metabolites were determined by infrared spectra, high-resolution mass spectrometry, proton nuclear magnetic resonance, and carbon-13 nuclear magnetic resonance.     

Biosynthesis of 3α,6β-ditigloyloxytropane and 3α,6β-ditigloyloxytropan-7β-ol in Datura

Datura meteloides; plants were fed with tiglic acid-[-¹⁴C] via the roots and after 2 days the percentage incorporation into the alkaloids 3α-tigloyloxytropane, 3α,6β-ditigloyloxytropane, meteloidine and 3α,6β-ditigloyloxytropan-7β-ol were 15·2, 1·82, 2·2 and 1·8 respectively. 3α,6β-Ditigloyloxytropane was partially hydrolysed to 6β-hydroxy-3α-tigloyloxytropane which contained 58·1% of the radioactivity of the original base, whereas 3α,6β-ditigloyloxytropan-7β-ol gave meteloidine containing only 9·2% of the original activity. The results suggest that the di- and tri-hydroxytropanes may be formed by different routes.     

4,4,14α-trimethyl 9β,19-cyclo-5α-26-homocholesta-24,26-dien-3β-ol: a potent mechanism-based inactivator of Δ- to Δ-sterol methyl transferase

The title compound (4A) was synthesized and tested as a mechanism-based inactivator of the sterol methyl transferase (SMT) enzyme from Prototheca wickerhamii. Using cycloartenol as substrate, 4A was found to exhibit time-dependent inactivation kinetics, generating a K_i value of 30 μM and K_inact value of 0.30 min⁻¹.     

Identification of (24S)-24-methylcholesta-5,22-dien-3β-ol as the major sterol of a marine cryptophyte and a marine prymnesiophyte

The major sterol in the two unicellular marine algae Cryptomonas sp. and Isochrysis galbana has been identified as (24S)-24-methylcholesta-5,22-dien-3β-ol (epibrassicasterol). The production of a sterol with the 24α-configuration by cryptophycean and prymnesiophycean algae and by diatoms contrasts with the situation in many other algae which produce sterols with the 24β-configuration.     

The time-dependent inactivation of aromatase by 17β-hydroxy-10-methylthioestra-1,4-dien-3-one

17β-Hydroxy-10-methylthioestra-1,4-dien-3-one is an active-site irreversible inhibitor of aromatase, the cytochrome P-450 dependent enzyme responsible for the conversion of androst-4-ene-3,17-dione to estrone. Two time-dependent pathways to inactivation are observed, one of which requires NADPH activation.     

Synthesis of 3β-hydroxy-androsta-5,7-dien-17-one from 3β-hydroxyandrost-5-en-17-one via microbial 7α-hydroxylation

The synthesis of 3β-hydroxy-androsta-5,7-dien-17-one from 3β-hydroxy-androst-5-en-17-one (dehydroepiandrosterone, DHEA) via microbial 7α-hydroxylation has been accomplished. At the first stage, 3β,7α-dihydroxy-androst-5-en-17-one was obtained in high yield (71.2%) using a strain of Gibberella zeae VKM F-2600, which was first applied for DHEA conversion. The further route included the substitution of 7α-hydroxyl group with chlorine followed by a dehydrochlorination stage, and required minimal purifications of the intermediate products. The steroids obtained at every step were characterized by TLC_,¹H NMR, MS, UV- and IR-spectrometry.The combination of microbial and chemical steps ensured 54.6% yield of the target 3β-hydroxy-androsta-5,7-dien-17-one from DHEA and can be applied for obtaining novel vitamin D derivatives.     

Cycloart-25-en-2β-ol from Euphorbia nivulia

A new tetracyclic triterpene cycloart-25-en-3β-ol (9β,19-cyclolanost-25-en-3β-ol) and cyclolaudenol, have been isolated from Euphorbia nivulia.     

Cell specific steroid inhibitions in histochemical steroid 3β-ol dehydrogenase activities in man

Summary Histochemical evidence is presented for the occurrence of specific steroid 3-ol dehydrogenase activities in steroidogenic cells of the human ovary, testes and adrenal. The enzymes in the cells of the corpus luteum and adrenal show similar dehydrogenase reactions with some steroid substrates and are inhibited by progesterone, a known physiologic steroid. Theca cells have an activity which is less readily demonstrated and apparently inhibited by both progesterone and DHA. The ovarian hilus cells and the interstitial cells of the testis contain steroid dehydrogenase activity which is inhibited by DHA and not by progesterone. The cellular specificity suggests that the type of activity plays a major role in determining the type of hormone production. The specificity of the steroid inhibitors suggests the possibility of intracellular feedback mechanisms which control the amount of hormone produced.Supported by USPHS Grant No. AMO 3806-07.     

Spirostanoids with 1,4-dien-3-one or 3β,7α-diol-5,6-ene moieties from Solanum violaceum

Bioassay-guided fractionation of the CHCl₃ layer of Solanum violaceum areal parts methanolic extract led to the isolation of four new steroidal sapogenins, indiosides L–O (1–4), along with eight known steroids, one lignin, and a coumarin. Indioside L is a rare spirostanoid possessing a 1,4-dien-3-one moiety in ring A. Moreover, compounds 3 and 4 represent rare examples of spirostene with the 3β,7α-diol-5,6-ene moiety compared to the normal 3β,7β-diol-5,6-ene derivatives. The cytotoxic activity of the isolates (5–14) was evaluated against human hepatoma (HepG2 and Hep3B), human lung carcinoma (A549), and human breast carcinoma (MDA-MB-231 and MCF-7).     

Sterol synthesis. Synthesis of 15-oxygenated 5α, 14β-cholest-7-en-3β-ol derivatives

Treatment of 3β-benzoyloxy-14α, 15α-epoxy-5α-cholest-7-ene with boron trifluoride-etherate gave, in 43% yield, 3β-benzoyloxy-5α, 14β-cholest-7-en-15-one with the unnatural C ring juncture. Reduction of the latter compound with lithium aluminum hydride gave 15α, 14β-cholest-7-en-3β, 15α-diol and 5α, 14β-cholest-7-en-3β, 15β-diol in 9% and 81% yields, respectively.