- A Novel Synthesis of Brassinolide and Related Compounds
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A stereoselective synthesis of the natural promoting steroids, brassinolide, homobrassinolide, and typhasterol is described, which involves construction of a side chain by lactonisation of Z-(5) under acidid conditions to give an α,β-unsaturated δ-lactone (6) with the inversion of the configuration at C-22 of the epoxy steroid in quantitative yield.
- Wei-Shan, Zhou,Jiang, Biao,Pan, Xin-fu
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- STEREOSELECTIVE SYNTHESIS OF THE BRASSINOLIDE SIDE CHAIN: NOVEL SYNTHESIS OF BRASSINOLIDE AND RELATED COMPOUNDS
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A stereoselective synthesis of the brassinolide side chain involves the lactonization of Z-10 under acidic condition to give an α,β-unsaturated-δ-lactone 11 with the inversion of the configuration at C-22 of the epoxy steroid in quantitative yield.The 22R,23R,24R-γ-hydroxy-δ-lactone 14 was used as key intermediate for the syntheses of brassinolide (1), homobrassinolide (2), and typhasterol (4) as well as the side chain of the dolicholide (3).
- Zhou, Wei-shan,Jiang, Biao,Pan, Xin-fu
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- The development and use of a general route to brassinolide, its biosynthetic precursors, metabolites and analogues
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A new method for the construction of steroid side chains through the addition of lithium salts of dithianes to a C-22 aldehyde was developed. An efficient one-pot procedure for the preparation of a suitable C-22 aldehyde from commercial epibrassinolide in three steps in 86% isolated yield was described. Enantioselective hydroxymethylation of isovaleraldehyde and Kulinkovich cyclopropanation of silylated Roche esters were used as key steps for the dithiane syntheses. The method was applied for the preparation of brassinolide, its biosynthetic precursors and metabolites. In addition, a number of brassinosteroids with a double bond in the side chain were prepared as precursors for tritiated derivatives for biosynthetic studies.
- Hurski,Ermolovich,Zhabinskii,Khripach
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p. 1446 - 1452
(2015/01/30)
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- A general approach to synthesis of labeled brassinosteroids: Preparation of [25,26,27-2h7]brassinolide with 60% isotopic purity from the parent brassinolide
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From brassinolide (BL) 1, [25,26,27-2H(n)]BL 10 was synthesized in 5 steps including C-25 hydroxylation, dehydration and catalytic deuteriogenation. In direct oxy-functionalization of tetra-O-acetyl BL 2 with methyl(trifluoromethyl)dioxirane leading to 25-hydroxyl compound 3, 14- hydroxyl, 25-hydroxy-15-oxo and 14,25-dihydroxyl derivatives, 4, 5 and 6, were newly identified; the catalytic deuteriogenation of Δ(25(26))-BL 8 using 5% palladium-on-charcoal resulted in abundant incorporation of deuterium atoms to give 10 with 60% isotopic purity of [25,26,27-2H7]BL.
- Seto, Hideharu,Fujioka, Shozo,Koshino, Hiroyuki,Yoshida, Shigeo,Watanabe, Tsuyoshi,Takatsuto, Suguru
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p. 7525 - 7528
(2007/10/03)
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- Improved synthesis of brassinolide
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Brassinolide has been synthesized from stigmasterol in an overall yield of 7%. The key step in the synthesis is aldol condensation of 2α,3α-isopropylidenedioxy-6-oxo-23,24-dinor-5α-cholan-22-al with 3-isopropylbut-2-enolide carried out at -78°C, which gives a product with 22R,23R stereochemistry in high yield. Catalytic hydrogenation of this product is highly stereoselective leading to the desired 245 stereochemistry in an intermediate which is readily transformed into brassinolide. Copyright 1996 by the Royal Society of Chemistry.
- McMorris, Trevor C.,Chavez, Rodrigo G.,Patil, Prakash A.
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p. 295 - 302
(2007/10/03)
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- SYNTHESIS OF BRASSINOLIDE AND ITS ANALOGS
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A new version of the synthesis of brassinosteroids of the 28C series is described.It is based on stigmasterol and uses the reaction of steroidal 22-aldehydes with aryl sulfones.
- Khripach, V. A.,Zhabinskii, V. N.,Ol'khovik, V. K.,Lakhvich, F. A.
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p. 1699 - 1706
(2007/10/02)
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- STEREOCONTROLLED SYNTHESIS OF THE BRASSINOLIDE SIDE CHAIN VIA A PYRANONE DERIVATIVE
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A new method for assembling the brassinolide side chain from 20-carboxaldehyde 2 was developed via the stereoselective construction of the pyranone moiety as key steps.
- Kametani, Tetsuji,Keino, Katsuyuki,Kigawa. Masaharu,Tsubuki, Masayoshi,Honda, Toshio
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p. 3141 - 3142
(2007/10/02)
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- 3α,5-cyclo-22,23-dihydroxy-5α-steroid compounds
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New steroid compounds of the general formula: STR1 wherein X is a hydroxyl group and Y is a hydrogen atom, or X and Y, taken together, form an oxo group; each of the two R' radicals is independently a hydrogen atom, acyl group, a silyl group, an alkoxycarbonyl group or a benzyl group, or the two R' radicals, taken together, form an alkylidene or a carbonyl group, the stereo-configuration at the 22- and 23-positions being either 22R and 23R or 22S and 23S; and R" and R'" are independently of each other a hydrogen atom or a lower alkyl group, as well as processes for preparing same. These new steroid compounds are valuable intermediates for brassinolide and its analogues useful as plant hormones.
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- Facile Syntheses of Brassinosteroids: Brassinolide, Castasterone, Teasterone and Typhasterol
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(22R,23R,24S)-3α,5-Cyclo-22,23-diacetoxy-5α-ergostan-6-one (2b) is a new key intermediate of some naturally occuring brassinosteroids such as brassinolide (1a), castasterone (1b), teasterone (1c) and typhasterol (1d).The cycloketone 2b was prepared in 10 steps via (22R,23R,24S)-6β-benzyloxy-3α,5-cyclo-22,23-dihydroxy-5α-ergostane (5) from stigmasterol. 2b was treated with a catalytic amount of p-toluenesulfonic acid and sodium bromide to give an enone (7b), which was oxidized with osmium tetroxide and derived to give a 2α,3α-acetonide (8b). 8b was easily separated from its isomer by the use of silica gel column chromatography. 8b was oxidized with trifluoroperacetic acid and deacetylated to give 1a. 8b was deacetylated and deacetonized to give 1b. 2b was treated with dilute sulfuric acid in acetic acid to give a 3β-acetate (10). 10 was treated with sodium hydroxide to give 1c. 2b was treated with hydrobromic acid to give a 3β-bromide (12), which was treated with silver acetate to give a 3α-acetate (13). 13 was treated with sodium hydroxide to give 1d.
- Aburatani, Masakazu,Takeuchi, Tadashi,Mori, Kenji
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p. 1909 - 1914
(2007/10/02)
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- Structural Revision of the Acetal Intermediates in Brassinolide Synthesis
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Acetalization of a steroidal ketone possessing an isopropylidenedioxy moiety in the other part of the molecule by acetal exchange with 2-ethyl-2-methyl-1,3-dioxolane was found to give an acetal with a sec-butylidenedioxy moiety.By this additional exchange reaction, a new chiral center was generated in the sec-butylidenedioxy moiety, and hence an unnecessary stereochemical complexity was added.To circumvent the problem, 2,2-dimethyl-1,3-dioxolane was employed for the acetalization.By adopting this procedure, several intermediates in Mori's brassinolide synthesis could be obtained in pure and crystalline states.The present improved synthesis furnished 30 g of brassinolide in a 7.0percent overall yield from stigmasterol, in contrast to 3.0percent by the original procedure.
- Aburatani, Masakazu,Takeuchi, Tadashi,Mori, Kenji
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p. 3557 - 3562
(2007/10/02)
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- Stereoselective Synthesis of Plant Growth-promoting Steroids, Brassinolide, Castasterone, Typhasterol, and Their 28-Nor Analogues
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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-ergostan-6-one, 28-norbrassinolide (1b), (22R,23R)-2α,3α,22,23-tetrahydroxy-B-homo-7-oxa-5α-cholestan-6-one, brassinone (2b), (22R,23R)-2α,3α,22,23-tetrahydroxy-5α-cholestan-6-one, and typhasterol (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.
- Takatsuto, Suguru,Yazawa, Naoto,Ishiguro, Masaji,Morisaki, Masuo,Ikekawa, Nobuo
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p. 139 - 146
(2007/10/02)
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- SYNTHESIS OF (22S,23S)-HOMOBRASSINOLIDE AND BRASSINOLIDE FROM STIGMASTEROL
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(22S, 23S)-Homobrassinolide (2α, 3α, 22S, 23S-tetrahydroxy-24S-ethyl-B-homo-7-oxa-5α-cholestan-6-one) and brassinolide (2α, 3α, 22R, 23R-tetrahydroxy-24S-methyl-B-homo-7-oxa-5α-cholestan-6-one) were synthesized from stigmasterol and shown to promote plant growth.
- Mori, Kenji,Sakakibara, Masayuki,Ichikawa, Yoshitaka,Ueda, Hiraki,Okada, Katsuhide,et al.
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p. 2099 - 2110
(2007/10/02)
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- Synthesis and biological activity of brassinolide and its 22 beta, 23 beta-isomer: novel plant growth-promoting steroids.
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Brassinolide (2 alpha, 3 alpha, 22 alpha, 23 alpha-tetrahydroxy-24 alpha-methyl -B-homo-7-oxa-5 alpha-cholestan-6-one), a novel plant growth-promoting steroid isolated from rape pollen, and its hitherto unknown 22 beta, 23 beta-isomer were synthesized from a C-24 epimeric 60:40 mixture of 22-dehydroxampesterol (24 alpha-methyl) and brassicasterol (24 beta-methyl) from oysters. The method of synthesis favored the formation of the 22 beta, 23 beta-isomer by better than 4:1. Comparative plant growth-promoting capabilities of brassinolide, both natural and synthetic, and its three side chain cis-glycolic isomers in the bean second internode bioassay showed that the natural and synthetic brassinolides were equally active and caused splitting of the internode at the 0.1 microgram level. The least active was the 22 beta, 23 beta-isomer of brassinolide. The isomers with the 22 alpha, 23 alpha and 24 alpha, and the 22 beta, 23 beta and 24 beta configurations were highly active and were required at about 10 times the concentration of brassinolide to cause the same physiological response. In the bean first internode bioassay, an auxin-induced growth test system which employs isolated bean plant segments, the isomer with 22 beta, 23 beta and 24 beta configuration caused a greater response than brassinolide. Two of the four tetrahydroxy ketones obtained in the synthesis of the isomers were also active in both assays.
- Thompson,Mandava,Meudt,Lusby,Spaulding
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p. 567 - 580
(2007/10/02)
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