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Stereochemistry of Hydride Reduction of 20-Hydroxyecdysone Derivatives

“…To a solution of 0.2 g (0.28 mmol) of compound IV (prepared according to [6], mp 48-50°C) in 2 ml of MeOH we added under stirring 0.14 g (0.39 mmol) of CeCl 3 · 6 H 2 O, the mixture was cooled to -5°C, and 0.02 g (0.6 mmol) of NaBH 4 was added. The mixture was warmed up to room temperature, stirred for 0.5 h, and evaporated under reduced pressure, and the residue was subjected to column chromatography on silica gel (6 g; CHCl 3 -MeOH, 10 : 1) to isolate 0.1 g (59%) of compound V, R f 0.54 (CHCl 3 -MeOH, 10 : 1) (a mixture of 6α-and 6β-epimers at a ratio of ~3 : 2, according to the 1 H NMR data: δ 4.55 and 3.78 ppm for 6-H in 6α-and 6β-epimer, respectively), and 0.05 g (25%) of VI, R f 0.3 (CHCl 3 -MeOH, 10:1) (a mixture of 6α-and 6β-epimers at a ratio of ~3 : 2, according to the 1 H NMR data: δ 4.59 and 3.82 ppm for 6-H in 6α-and 6β-epimer, respectively).…”

“…Compound IV was synthesized by reaction of I with Me 3 SiCF 3 in the presence of tetrabutylammonium fluoride (cf. [6]). The reduction of IV was accompanied by partial deprotection of the 25-OH group.…”

Ozonolysis of Alkenes and Study of Reactions of Polyfunctional Compounds: LXVII. Synthesis of 27,27,27-Trifluoro-20-hydroxyecdysone Acetonides from 24,25- and 25,26-Anhydro-20-hydroxyecdysone Derivatives via Ozonolysis and Trifluoromethylation

“…The yield of ketone III obtained by the procedure described in [7] was greater than in the synthesis by ozonolysis [8] which was used by us previously [1] for the same purpose. By treatment with Me 3 SiCF 3 in the presence of Bu 4 N + F -(according to [9]) compounds I and III were converted into the corresponding 14-O-trimethylsilyl derivatives II and V. As followed from the intensity ratio of the signals from C 25 =C 24 H (δ 5.18 ppm, t, 3 J = 7.0 Hz) and C 25 =C 26 H 2 (δ 4.71 and 4.75 ppm, two singlets) in the 1 H NMR spectrum of II, the ratio of the ∆ 24,25 -and ∆ 25,26 -moieties is equal to ~2 : 1. Ozonolysis of silyl derivative II under different conditions (by the procedures reported in [7,8,10]) led to formation of a complex mixture of products.…”

“…Alcohol IX showed in the 13 C NMR spectrum a signal at δ 61.4 ppm, which is typical of carbon atom at the primary hydroxy group (C 24 H 2 OH). Alcohol IX was converted into the corresponding 14,24-bis(trimethylsilyl) ether X according to the procedure described in [9]. The 1 H and 13 C NMR spectra of X contained the following signals: δ C 1.9 (14-OSiMe 3 ), 0.6 ppm (24-OSiMe 3 ) and δ 0.10 (9H, 14-OSiMe 3 ), 0.09 ppm (9H, 24-OSiMe 3 ) (cf.…”

“…The 1 H and 13 C NMR spectra of X contained the following signals: δ C 1.9 (14-OSiMe 3 ), 0.6 ppm (24-OSiMe 3 ) and δ 0.10 (9H, 14-OSiMe 3 ), 0.09 ppm (9H, 24-OSiMe 3 ) (cf. [9,11]). …”