A new synthesis of [26,28‐²H₆]brassinolide and [26,28‐²H₆]castasterone via an unusual methyl migration

Abstract

SummaryDeuterium-labelled brassinosteroids, namely ½26; 28-2 H 6 castasterone, 8, and ½26; 28-2 H 6 brassinolide, 9, were synthesized starting from 6; 6-ethylenedioxy-20-formyl-2a; 3a-isopropylidenedioxy-5a-pregnane, 1, and 3-½ 2 H 3 methyl-but-1-yne-½4; 4; 4-2 H 3 , 11. Upon alkylating cleavage of the epoxide 6 with trimethylaluminium-n-butyllithium an unusual migration of a neighbouring ½ 2 H 3 methyl group takes place to afford deuteriation at positions 26 and 28.

Cobalamin-Dependent Apparent Intramolecular Methyl Transfer for Biocatalytic Constitutional Isomerization of Catechol Monomethyl Ethers

“…The apparent intramolecular migration of methyl groups has been hardly investigated despite its important role in organic synthesis involving homogeneous and heterogeneous catalysis. 44−48 To the best of our knowledge, Me-Cbl-dependent enzymes have never been described before to catalyze an isomerization reaction; these reactions are usually encountered in the repertoire of their Ado-Cbl-dependent analogue.…”

“…In the present study, we report an apparent intramolecular methyl group transfer resulting in constitutional substrate isomerization employing the cobalamin-dependent MTase from D. hafniense . The apparent intramolecular migration of methyl groups has been hardly investigated despite its important role in organic synthesis involving homogeneous and heterogeneous catalysis. − To the best of our knowledge, Me-Cbl-dependent enzymes have never been described before to catalyze an isomerization reaction; these reactions are usually encountered in the repertoire of their Ado-Cbl-dependent analogue.…”

Reversible Conversion In The Brassinosteroid Quartet Castasterone, Brassinolide And Their 3β-Epimers

“…Using this approach, castasterone (1), brassinolide (2), 3-epicastasterone (3) and 3-epibrassinolide (4) were detected in Arabidopsis seedlings. The relative retention times of authentic standards and mass spectral data ( [33] were administered in a series of separate experiments in different plant materials, seedlings of A. thaliana S. cereale, and cell suspension cultures of L. esculentum. After a two-day incubation, the plant material was extracted according to the procedure used to detect endogenous brassinosteroids.…”

Steroids: reactions and partial synthesis

“…The brassinolide plant hormones have continued to attract interest with reports on novel methods of constructing the side chain, 126 and the synthesis of B-homo analogues, 127 C-28 homo analogues, 128 and labelled brassinolides. 129 The anti-tumour activity of the marine sterol aragusterol A has provided the stimulus for the synthesis 130 of some analogues, 37, from cholic acid. The tumour-inhibiting properties of the dimeric steroids of the cephalostatin series has also continued to stimulate synthetic methodology.…”