New Route for the Synthesis of (22S,23S)-28-Homobrassinolide

Abstract

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.

Key words

brassinosteroids - dihydroxylation - plant growth promoters - ruthenium tetroxide - sodium perborate

References

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12

Godrej Agrovet Ltd. Mumbai, India, has commercialised (22S,23S)-homobrassinolide for the enhancement of yields of paddy, wheat, tomato, cabbage, cauliflower, potato, groundnut (peanut), cotton, grapes and tea.