- Synthesis and preliminary evaluation of dimeric-28-homobrassinosteroids for plant growth regulators
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Preparation of synthetic analogues of 28-homobrassinosteroids is reported. Also, the addition of the 28-homocastasterone at the C6 carbonyl group via allyl Gringard reagent followed by olefin cross metathesis resulted in dimeric analogues. Rice lamina inclination assay showed that the replacement of the C6 carbonyl group by 6α-allyl and 6β hydroxyl groups led to a decrease in bioactivity, whereas the dimeric analogues showed a reduced but significant bioactivity when compared to the 28-homocastasterone.
- Phutdhawong, Waya S.,Ruensamran, Wanwikar,Phutdhawong, Weerachai
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- SYNTHESIS AND BIOLOGICAL ACTIVITY OF 28-HOMOBRASSINOLIDE AND ANALOGUES
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28-Homobrassinolide has been synthesized from stigmasterol in an overall yield of 21percent.The biological activity of 28-homobrassinolide, brassinolide, 24-epibrassinolide, 22S,23S,24-epibrassinolide, and 22S,23S,28-homobrassinolide have been compared in the soybean epicotyl elongation assay.All the steroids except 22S,23S,28-homobrassinolide exhibited a similar biological activity, but the latter compound was substantially less active.There appears to be a correlation between biological activity and overall dimensions of the steroidal side chain.
- McMorris, Trevor C.,Patil, Prakash A.,Chavez, Rodrigo G.,Baker, Michael E.,Clouse, Steven D.
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- New route for the synthesis of (22S,23S)-28-homobrassinolide
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A new and highly efficient synthesis of (22S,23S)-28-homobrassinolide (3) has been achieved. (2α,3α,22S,23S)-Tetrahydroxy-5α-stigmastan-6-one (4), a key intermediate for the synthesis of 3, and (2α,3α)-dihydroxy-5α-stigmast-22-en-6-one (6), a versatile intermediate for the synthesis of 3, and several naturally occurring brassinosteroids have been obtained in excellent yield from stigmasta-2,(22E)-dien-6-one (5) by catalytic RuO4 hydroxylation. Sodium perborate, a cheap and large-scale industrial chemical is used for Baeyer-Villiger oxidation of B-ring ketone 9 to its lactone 10.
- Massey, Archna P.,Pore, Vandana S.,Hazra, Braja G.
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p. 426 - 430
(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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