Synthesis of deuterium‐labeled (24R)‐methyl brassinosteroids

Abstract

Synthesis of labeled brassinosteroids (24-epibrassinolide and its biosynthetic precursors) containing three deuterium atoms in the terminal part of the side chain is reported. Labeling was achieved by three-step reductive transformation of carbethoxy group into methyl using lithium aluminium deuteride. The proposed method ensured high isotopic purity of (24R)-methyl brassinosteroids containing a label in a position which is not subjected to its loss.

Synthetic Aspects of Brassinosteroids

“…A large number of labeled BSs bearing three deuterium atoms in the side chain (examples are shown in Figure 6.1) were synthesized by Khripach et al [48][49][50][51][52]. Their carbon skeleton was constructed by Claisen rearrangement.…”

An improved synthesis of [26‐2H3]castasterone

“…Apart from high chemical and isotopic purity, an important prerequisite for a successful implementation of deuterium‐labeled BS as internal standards is the presence of at least three non‐exchangeable deuterium atoms in their molecules . A number of three and six deuterated analogs of BS were prepared, with labels at C‐22, C‐26, C‐27 and C‐28 . Although all these compounds are equally suitable for use in mass‐spectrometry analysis, preparation of labeled BS bearing three deuterium atoms at C‐26 is an easier task in comparison with preparing other deuterated BS .…”