Synthesis of [26-2H3]-6-deoxo-24-epicastasterone

Synthetic Aspects of Brassinosteroids

“…Treatment of the propanoyl ester (41) with an excess of LDA and Me 3 SiCl resulted first in the formation of rearranged product (42) that under the reaction conditions underwent C-25 silylation to afford silane (43) (Scheme 6.5) [29]. Both diastereomers (50) and (51) were available starting from the propanoyl ester (47) depending on the solvent (THF or a mixture of THF-HMPA) employed for the generation of the enolates (48) and (49) (Scheme 6.6) [30]. Both diastereomers (50) and (51) were available starting from the propanoyl ester (47) depending on the solvent (THF or a mixture of THF-HMPA) employed for the generation of the enolates (48) and (49) (Scheme 6.6) [30].…”

“…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.…”

Labelling of brassinosteroids by isotopes of hydrogen and carbon

“…Deoxygenation of at C-6 was done via methyl xanthate 130 and for nal cis hydroxylation potassium osmate was used. Thus, the 6-deoxo-24-[26-2 H 3 ]epiCS 132 was prepared 47 in overall yield 18% calculated on ester 125.…”

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 .…”