Masuo Morisaki

Synthesis of active forms of vitamin D. Part IX. Synthesis of 1α,24-dihydroxycholecalciferol

24-Oxocholesterol (1)(readily available from fucosterol) was converted by three steps into 1α,24ξ-dihydroxycholesterol (4). From the corresponding triacetate (5), 1α,24ξ-dihydroxycholecalciferol (9) was prepared via the 5,7-diene (8). The C-24 epimers of compound (4) were resolved by silica gel column chromatography of the monohydroxydibenzoates (7), and were separately transformed into the corresponding 1α,24-dihydroxycholecalciferol epimers.

Biosynthesis of sterols and ecdysteroids in Ajuga hairy roots

Hairy roots of Ajuga reptans var. atropurpurea produce clerosterol, 22-dehydroclerosterol, and cholesterol as sterol constituents, and 20-hydroxyecdysone, cyasterone, isocyasterone, and 29-norcyasterone as ecdysteroid constituents. To better understand the biosynthesis of these steroidal compounds, we carried out feeding studies of variously 2H- and 13C-labeled sterol substrates with Ajuga hairy roots. In this article, we review our studies in this field. Feeding of labeled desmosterols, 24-methylenecholesterol, and 13C2-acetate established the mechanism of the biosynthesis of the two C29-sterols and a newly accumulated codisterol, including the metabolic correlation of C-26 and C-27 methyl groups. In Ajuga hairy roots, 3α-, 4α-, and 4β-hydrogens of cholesterol were all retained at their original positions after conversion into 20-hydroxyecdysone, in contrast to the observations in a fern and an insect. Furthermore, the origin of 5β-H of 20-hydroxyecdysone was found to be C-6 hydrogen of cholesterol exclusively, which is inconsistent with the results in the fern and the insect. These data strongly support the intermediacy of 7-dehydrocholesterol 5α,6α-epoxide. Moreover, 7-dehydrocholesterol, 3β-hydroxy-5β-cholest-7-en-6-one (5β-ketol), and 3β,14α-dihydroxy-5β-cholest-7-en-6-one (5β-ketodiol) were converted into 20-hydroxyecdysone. Thus, the pathway cholesterol→7-dehydrocholesterol→7-dehydrocholesterol 5α,6α-epoxide→5β-ketol→5β-ketodiol is proposed for the early stages of 20-hydroxyecdysone biosynthesis. 3β-Hydroxy-5β-cholestan-6-one was also incorporated into 20-hydroxyecdysone, suggesting that the introduction of a 7-ene function is not necessarily next to cholesterol. C-25 Hydroxylation during 20-hydroxyecdysone biosynthesis was found to proceed with ca. 70% retention and 30% inversion. Finally, clerosterol was shown to be a precursor of cyasterone and isocyasterone.

Biosynthesis of 24β-alkyl-Δ25-sterols in hairy roots of Ajuga reptans var. atropurpurea

A hairy root culture of Ajuga reptans var. atropurpurea contains clerosterol, 22-dehydroclerosterol and cholesterol as its sterol constituents. Feeding of [26-, 27-13C2]desmosterol to this culture and 13C NMR analysis of the resulting biosynthesized sterols showed that the substrate was efficiently incorporated into clerosterol and codisterol. Feeding of [26-13C] and [27-13C]desmosterols revealed that the C-24 alkylation takes place in a highly specific manner wherein the 26- and 27-methyl groups of the substrate becomes C-26 (vinyl methyl) and C-27 (exomethylene carbon), respectively, of the two Δ25-sterols. Further, feeding of [24-2H]desmosterol and 2H NMR analysis of the products showed that H-24 of clerosterol and codisterol is derived from H-24 of desmosterol. Finally, [28-13C]ergosta-5,24(28)-dien-3β-ol was shown to be converted into clerosterol and 22-dehydroclerosterol, but not into codisterol. On the basis of these data, possible biosynthetic mechanism of 24β-alkyl-Δ25-sterols in this plant is proposed.

Studies on organic fluorine compounds. Part 37. Studies on steroids. Part 78. Synthesis of 24,24-difluoro- and 24ξ-fluoro-25-hydroxyvitamin D3

To clarify the physiological significance of C-24 hydroxylation in vitamin D3 metabolism, vitamin D3 compounds blocked at C-24 by fluorine substituents, namely 24,24-difluoro-25-hydroxyvitamin D3(1) and 24ξ-fluoro-25-hydroxyvitamin D3(2) have been synthesized from 3β-hydroxychol-5-en-24-oic acid (13).

Fucosterol-24,28-epoxide, as a probable intermediate in the conversion of β-sitosterol to cholesterol in the silkworm

3 H-Fucosterol-24,28-epoxide (V) was effectively incorporated into cholesterol (I) in the silkworm; it was also trapped in the insect as a probable intermediate in conversion of fucosterol (II) into cholesterol (I).

Biosynthesis of phytoecdysteroids in Ajuga hairy roots: clerosterol as a precursor of cyasterone, isocyasterone and 29-norcyasterone

Abstract Feeding studies of six 13 C-labeled sterols, including clerosterol, to hairy roots of Ajuga reptans var. atropurpurea have established that clerosterol is a precursor of three phytoecdysteroids, cyasterone, isocyasterone and 29-norcyasterone.

Synthesis of brassinolide, a steroidal lactone with plant-growth promoting activity

Brassinolide, a plant-growth promoter isolated from rape pollen, was stereoselectively synthesized from dinorcholenic acid.

Stereoselective synthesis of plant growth-prompting steroids, brassinolide, castasterone, typhasterol, and their 28-nor analogues

Plant growth-promoting steroids, brassinolide (1a), (22R,23R,24S)-2α,3α,22,23-tetrahydroxy-B-homo-7-oxa-5α-ergostan-6-one, castasterone (2a), (22R,23R,24S)-2α,3α,22,23-tetrahydroxy-5α-ergo-stan-6-one, 28-norbrassinolide (1b), (22R,23R)-2α,3α,22,23-tetrahydroxy-B-homo-7-oxa-5α-chole-stan-6-one, brassinone (2b), (22R,23R)-2α,3α,22,23-tetrahydroxy-5α-cholestan-6-one, and typh-asterol (2c), (22R,23R,24S)-3α,22,23-trihydroxy-5α.-ergostan-6-one, have been stereoselectively synthesized. These steroids show very strong biological activities in three different kinds of bioassays.

Stereochemistry of the reduction of 24-ethyldesmosterol to sitosterol in tissue cultures of Oryza sativa

Feeding of [26-13C]- and [27-13C]-24-ethyldesmosterols to cultured cells of Oryza sativa followed by 13C-NMR analysis of the biosynthesized sitosterol revealed that the reduction of 24(25)-double bond proceeds with an anti-addition of hydrogen atoms, thus the E-methyl group of the olefinic precursor becomes the pro-S-methyl on C-25 of sitosterol.

Synthetic studies of withanolides. Part I. Synthesis of 5,6β-epoxy-4β-hydroxy-5β-cholest-2-en-1-one and related compounds

The title compounds, which have functionalities in rings A and B similar to those of withaferin A(1), have been synthesized through the key intermediates cholesta-2,5-dien-1-one (10) and -2,4-dien-1-one (26). Electrophilic reactions of the steroidal 2,4-dien-1-one system were observed to occur stereoselectively on the β-side of the 4,5-double bond.