Synthesis Of Brassinolide Research Articles

A formal synthesis of brassinolide

Enzyme-catalysed differentiation of hydroxy groups in a C 2v-shaped tetraol-sulfide, combined with a E-stereoconvergent Ramberg-Bäcklund process, allowed to prepare pure (2 S)-2,3-dimethyl-1-iodobutane, which could be coupled with a 3,5-cyclopregnane-20-thiomethanol derivative so as to give an efficient precursor of the title vegetal hormone.

Concise, Improved Procedure for the Synthesis of Brassinolide and Some Novel Side-Chain Analogues

Concise, Improved Procedure for the Synthesis of Brassinolide and Some Novel Side-Chain Analogues

ChemInform Abstract: Highly Stereocontrolled Formal Synthesis of Brassinolide via Chiral Sulfoxide‐Directed SN2′ Reactions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

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 24S stereochemistry in an intermediate which is readily transformed into brassinolide.

Highly Stereocontrolled Formal Synthesis of Brassinolide via Chiral Sulfoxide-Directed SN2‘ Reactions

An efficient stereocontrolled methodology for the preparation of the four contiguous chiral centers of the brassinosteroid side chain is described. Allylic mesyloxy sulfinyl steroids have been found to undergo highly stereoselective SN2‘ displacements when treated with cyanocuprates that provide the required acyclic stereocontrol in the key C-24 position of the steroidal side chain. Preparation of a direct precursor of brassinolide 1, as well as a precursor of naturally occurring (24R)-epibrassinolide, (+)-18, is carried out in two additional steps utilizing asymmetric dihydroxylations of (22E)-olefins (+)-2 and (+)-17. In this manner, a formal synthesis of this plant growth promoter has been completed, and the extension of the scope of this methodology has been explored providing a straightforward route to this family of steroids. Alternative routes to the key olefin (+)-2 are also outlined. Improved selectivity in the addition to aldehyde 7 for the preparation of the Cram (22R)-allylic hydroxy sulfoxides is achieved by controlling the chirality at sulfur or by a condensation−symmetric oxidation sequence employing the analogous vinyl sulfide reagent 22.

Stereoselective synthesis of (22R, 23R, 24S)-3β-hydroxy-5-ene-22,23-dihydroxy-24-methyl-cholestane: A brassinolide intermediate from 16-dehydropregnenolone acetate.

A new synthesis of the important aldehyde 1 from easily available 16-Dehydropregnenolone acetate (16-DPA) in high yield is described. The aldehyde 1 is converted to trio] 24, involving a stereoselective generation of all the four chiral centers in the brassinolide side chain. The important features of this synthesis is stereospecific generation of the acetate 14 through ene reaction using three different catalysts as well as regioselective wittig reaction on the acetoxy aldehyde 20. Conversion of triol 24 to brassinolide is known, hence this constitutes a formal total synthesis of brassinolide.

ChemInform Abstract: Study on the Synthesis of Brassinolide and Related Compounds. Part 15. Formal Synthesis of Brassinolide via Stereoselective Sulfenate‐ Sulfoxide Transformation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Studies on steroidal plant-growth regulator 25. Concise stereoselective construction of sidechain of brassinosteroid from the intact sidechain of hyodeoxycholic acid: formal syntheses of brassinolide, 25-methylbrassinolide, 26, 27-bisnorbrassinolide and their related compounds

A concise stereoselective construction of sidechain of brassinolide ( 1), 25-methylbrassinolide ( 3) and 26, 27-bisnorbrassinolide ( 4), which involves β-alkylative 1,3- carbonyl transposition of the α,gb-unsaturated ketones 11 and 34 and α, β-unsaturated methyl ester 26, using the intact sidechain of hyodeoxycholic acid ( 2) as starting material, is described. The formal syntheses of 1, 3 and 4 were accomplished. In the mean time, 25-methylcastasterone ( 21), 26,27-bisnortyphasterol( 6) and the new 25-methyltyphasterol ( 5) were also synthesized.

Studies on steroidal plant-growth regulator 21. A stereoselective construction of brassinosteroid side chain: a new practical synthesis of brassinolide and its analogues

Abstract The high stereoselectivity in osmium tetroxide catalyzed asymmetric dihydroxylation of Δ 22(23)-methyl hyodeoxycholate has been achieved, and the utilizing of (22R,23S)-22,23-dihydroxy methyl hyodeoxycholate as starting material for syntheses of brassinolide and its analogues is described.

ChemInform Abstract: Synthesis of Brassinolide and Its Analogues.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Study on the synthesis of brassinolide and related compounds. Part 15. Formal synthesis of brassinolide via stereoselective sulphenate–sulphoxide transformation

A formal synthesis of the natural growth-promoting steroid brassinolide is described, which involves construction of (22R,23E)-24-methyl-5β-cholest-23-ene-3α,6α,22-trio by methylation of (24R) and (24S)-(22E)-24-phenylsulphinyl-5β-cholest-22-ene-3α,6α-diol followed by 1,3-sulphoxidehydroxy transposition.

Synthesis of castasterone and formal synthesis of brassinolide from stigmasterol via a selenosulfonation approach

Synthese de castasterone a partir d'(6,6-ethylenedioxy-2,3-isopropylidenedioxy) pregnane-20-carbaldehyde, de (3-[trimethylsilyl]propargyl) lithium et de p-tolueneselenosulfonate de Se phenyle

ChemInform Abstract: Stereoselective Synthesis of the Brassinolide Side Chain: Novel Syntheses of Brassinolide and Related Compounds.

AbstractThe brassinolide side chain is synthesized stereoselectively following the reaction sequence (I) → (VII).

ChemInform Abstract: Syntheses of Brassinolide and Related Compounds. Part 14. Highly Stereoselective Construction of the Side‐Chain of Brassinosteroids Utilizing the β‐Alkylative 1,3‐Carbonyl Transposition of the Steroidal 22‐En‐24‐one.

AbstractThe overall yield of (X) from (I) is 47%.

Study on the synthesis of brassinolide and related compounds: XIV. β‐alkylative 1,3‐carbonyl transposition of the steroidal 22‐en‐24‐one: A new practical route to the side chain of the plant growth promoter, brassinosteroid

Study on the synthesis of brassinolide and related compounds: XIV. β‐alkylative 1,3‐carbonyl transposition of the steroidal 22‐en‐24‐one: A new practical route to the side chain of the plant growth promoter, brassinosteroid

Stereoselective synthesis of the brassinolide side chain; novel syntheses 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-unsa-turated-δ-lactone 11 with the inversion of the configuration at C-22 of the epoxy steroid in quantitative yield. The 22R,23R,24S-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).

Study on the syntheses of brassinolide and related compounds. Part 14. Highly stereoselective construction of the side-chain of brassinosteroids utilizing the β-alkylative 1,3-carbonyl transposition of the steroidal 22-En-24-one

A stereoselective synthesis of the side-chain of brassinolide which involves β-alkylative 1,3-carbonyl transposition of the α,β-unsaturated ketone 3,6-diacetoxycholest-22-en-24-one is described. The overall yield of (22R,23R,24S)-22,23-isopropylidenedioxy-24-methyl-5β-cholestane-3α,6α-diol from 3α,6α-diacetoxy-5β-pregnane-20-carbaldehyde in six steps is 47%.

Highly stereoselective synthesis of steroidal 22α-allylic alcohols via 22-aldehydes and 1-silyl-1-iodo-1-alkenes: A new efficient route to the side chain construction of brassinolide

1-Lithium-1-(trimethylsilyl)-3-methyl-1-butene 9 undergoes smooth addition with aldehyde 10 to give 22α-alcohol 11 as a major product. Desilylation of 11 and further oxidation of 14 by MCPBA leads to epoxyalcohol 16 suitable for brassinolide synthesis.

ChemInform Abstract: A Novel Synthesis of Brassinolide and Related Compounds.

ChemInform Abstract: A Novel Synthesis of Brassinolide and Related Compounds.

A selenosulfonation-based approach to (22S,23E)-6β-methoxy-3α,5-cyclo-5α-ergost-23-en-22-ol, a key intermediate for brassinolide synthesis

(22S,23E)-6β-Methoxy-3α,5-cyclo-5α-ergost-23-en-22-ol (2), an intermediate in the synthesis of brassinolide (μ) and related compounds, was synthesized by a new approach. (20S)-6β-Methoxy-3α,5-cyclo-5α-pregnane-20-carboxaldehyde (5) was converted to the corresponding 22S and 22R-24-yn-22-ol derivatives 6a and 6b by treatment with 3-lithio-1 -trimethylsilylpropyne, followed by tetra-n-butylammonium fluoride. The products were subjected to selenosulfonation, base-catalyzed isomerization, and selenoxide elimination to afford the respective 22S and 22R allenic sulfones 9a and 9b. The 22S isomer 9a underwent addition with lithium diisopropylcuprate – dimethyl sulfide complex, followed by reductive desulfonylation with magnesium in methanol, to afford 2, as well as smaller amounts of its 24(28) isomer 11a and (22E)-6β-methoxy-3α,5-cyclo-5α-ergosta-22,24(28)-diene (12). Similar treatment of 9b afforded 13, the 22R isomer of 2, as the principal product, as well as its 24(28) isomer 11b, and diene 12. Keywords: brassinolide, (22S,23E)-6β-methoxy-3α,5-cyclo-5α-ergost-23-en-22-ol, selenosulfonation, allenic sulfones.