METHOD OF PRODUCING 24-EPIBRASSINOLIDE Russian patent published in 2025 - IPC C07J63/00 C07J73/00 

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing 24-epibrassinolide (22R,23R,24R)-2α,3α,22_,23-tetrahydroxy-B-homo-7-oxa-5α-ergostan-6-one corresponding to the formula given below, which is a plant growth regulator and a plant abiogenic stress modulator. Proposed method comprises steps 1)-7). At stage 1) mesylate (methanesulphonate) of ergosterol is synthesized by reaction of natural sterol, available commercial raw material, with methanesulphonyl chloride in dry pyridine at temperature of reaction medium not higher than +10 °C. At step 2) isoergosterol is synthesized by solvolytic isosteroid rearrangement by controlled hydrolysis of mesylate in aqueous solubilizing medium of high capacity (microemulsion system of the third type, consisting of water with addition of cationic surfactant, which is cetyltrimethylammonium bromide C₁₆H₃₃N(CH₃)₃Br, and cosolubilizer, aliphatic (C₂-C₅)-alcohol, in an amount of not more than 5% by volume) in the presence of sodium bicarbonate as a buffer agent and a balancing electrolyte. At step 3) isoergosterone is synthesized by oxidation of isoergosterol with a complex of chromic anhydride with pyridine in pyridine. At step 4), 7,8-dihydroisoergosterone is synthesized by reducing isoergosterone with technical sodium dithionite in a high-capacity aqueous solubilizing medium (a microemulsion system of the third type consisting of water with addition of a cationic surfactant which is cetyltrimethylammonium bromide C₁₆H₃₃N(CH₃)₃Br, and cosolubilizer, aliphatic (C₂-C₅)-alcohol, in an amount of not more than 5% by volume) in the presence of sodium bicarbonate as a buffer agent and a balancing electrolyte. At step 5), reverse steroidal (cyclopropylmethyl-homoallyl) rearrangement of 7,8-dihydroisoergosterone is performed with formation of (22E,24R)-5α-ergosta-2,22-dien-6-one by heating with catalytic amounts of anhydrous lithium bromide and pyridinium hydrochloride in dry dimethylacetamide. At step 6) synthesis of 24-epicastasterone is performed by asymmetric dihydroxylation of (22E,24R)-5α-ergosta-2,22-dien-6-one in the presence of a potassium osmate catalyst system - ligands DHQD-PHAL (hydroquinidine 1,4-phthalazinediyl diester) and hydroquinidine 4-chlorobenzoate, a stoichiometric oxidant of potassium hexacyanoferrate (III), methanesulfonamide, potassium carbonate in a tert-butanol-water two-phase medium. At step 7), 24-epicastasterone is oxidised with trifluoroacetic acid formed by mixing trifluoroacetic anhydride and 50% hydrogen peroxide in a medium of dry chloroform, with extraction and purification of the end product.

EFFECT: disclosed method enables to obtain 24-epibrassinolide with high total output using an improved technique.

1 cl, 7 ex