A general approach to synthesis of labeled brassinosteroids:: Preparation of [25,26,27-2H7]brassinolide with 60% isotopic purity from the parent brassinolide

From brassinolide (BL) 1, [25,26,27-H-2(n)]BL 10 was synthesized in 5 steps including C-25 hydroxylation, dehydration and catalytic deuteriogenation. In direct oxy-functionalization of tetra-O-acetyl BL 2 with methyl(trifluoromethyl)dioxirane leading to 25-hydroxyl compound 3, 14-hydroxyl, 25-hydroxy-15-oxo and 14,25-dihydroxyl derivatives, 4, 5 and 6, were newly identified; the catalytic deuteriogenation of Delta(25(26))-BL 8 using 5% palladium-on-charcoal resulted in abundant incorporation of deuterium atoms to give 10 with 60% isotopic purity of [25,26,27-H-2(7)]BL. (C) 1998 Elsevier Science Ltd. All rights reserved.