- SYNTHESIS OF NATURALLY OCCURRING BRASSINOSTEROIDS EMPLOYING CLEAVAGE OF 23,24-EPOXIDES AS KEY REACTIONS. SYNTHESIS OF BRASSINOLIDE, CASTASTERONE, DOLICHOLIDE, DOLICHOSTERONE, HOMODOLICHOLIDE, HOMODOLICHOSTERONE, 6-DEOXOCASTASTERONE AND 6-DEOXODOLICHOSTERONE
-
Eight new plant growth-promoting steroids (brassinolide, castasterone, dolicholide, dolichosterone, homodolicholide, homodolichosterone, 6-deoxocastasterone and 6-deoxodolichosterone) were synthesized by the regio- and stereoselective ring-opening reactions of 23,24-epoxides prepared from stigmasterol.
- Mori, Kenji,Sakakibara, Masayuki,Okada, Katsuhide
-
-
Read Online
- New Synthesis of Castasterone
-
An improved synthesis that could produce gram quantities of castasterone was proposed. The starting material was stigmasterol, the cyclic part of which was transformed in the first synthetic step into the 3α,5-cyclo-6-ketone. The side-chain carbon skeleton in the target compound was constructed with the required stereochemistry of the C-24 methyl via addition of methylacetylene, hydrogenation of the propargyl alcohol over Lindlar catalyst, and Claisen rearrangement. Diols were introduced using Sharpless asymmetric dihydroxylation of the intermediate ?2,22-dienone in the presence of (DHQD)2AQN. A unique feature of the synthesis was the avoidance of chromatographic separations of propargyl alcohols with similar chromatographic mobilities because the C-22 diastereomers were enriched in subsequent redox reactions.
- Khripach,Zhabinskii,Gurskii,Kolosova,Gulyakevich,Konstantinova,Antonchik,Pap
-
p. 117 - 123
(2018/02/19)
-
- Improved Synthesis of Castasterone and Brassinolide
-
Castasterone 1 is synthesized in 32% overall yield in eight steps from the known (20S)-6,6-ethylenedioxy-20-formyl-3x,5-cyclo-5x-pregnane 4.
- Watanabe, Tsuyoshi,Takatsuto, Suguru,Fujioka, Shozo,Sakurai, Akira
-
p. 360 - 361
(2007/10/03)
-
- Improved synthesis of brassinolide
-
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.
-
p. 295 - 302
(2007/10/03)
-
- Stereoselective Synthesis of Plant-Growth-Regulating Steroids: Brassinolide, Castasterone, and their 24,25-Substituted Analogues
-
Brassinosteroids and their congeners, brassinolide 1, castasterone 2, 25-methylbrassinolide 3, 25-methylcastasterone 4 and (24R)-24-phenylbrassinone 5, have been stereoselectively synthesized by employing the pyranone derivative 19 as a versatile intermediate for the construction of the side chain.
- Tsubuki, Masayoshi,Keino, Katsuyuki,Honda, Toshio
-
p. 2642 - 2650
(2007/10/02)
-
- A concise stereoselective synthesis of castasterone
-
A stereoselective synthesis of a brassinosteroid, castasterone, has been achieved by employing a pyranone derivative as a side-chain precursor.
- Honda,Keino,Tsubuki
-
p. 650 - 652
(2007/10/02)
-
- STEREOSELECTIVE SYNTHESIS OF THE BRASSINOLIDE SIDE CHAIN: NOVEL SYNTHESIS OF BRASSINOLIDE AND RELATED COMPOUNDS
-
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
-
p. 3173 - 3188
(2007/10/02)
-
- SYNTHESIS OF BRASSINOLIDE AND ITS ANALOGS
-
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.
-
p. 1699 - 1706
(2007/10/02)
-
- Facile Syntheses of Brassinosteroids: Brassinolide, Castasterone, Teasterone and Typhasterol
-
(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
-
p. 1909 - 1914
(2007/10/02)
-
- Structural Revision of the Acetal Intermediates in Brassinolide Synthesis
-
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
-
p. 3557 - 3562
(2007/10/02)
-
- Stereoselective Synthesis of Plant Growth-promoting 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-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
-
p. 139 - 146
(2007/10/02)
-
- Synthesis and biological activity of brassinolide and its 22 beta, 23 beta-isomer: novel plant growth-promoting steroids.
-
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
-
p. 567 - 580
(2007/10/02)
-