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Treatment of steroid sapogenins with benzaldehyde and BF 3 ·Et 2 O cleanly produces E-23(23′)-benzylidenspirostanes in good yields in a reaction pathway which consists on an aldol reaction followed by a dehydration step. The obtained E-23(23′)-benzylidenspirostanes can be easily converted to dinorcholanic lactones by treatment with CrO 3 in acetic acid. The synthetic sequence...
In addition to a previous report, the reaction of tigogenin acetate with ICl in refluxing CHCl 3 produced the hitherto unknown 23R-iodotigogenin acetate, bearing an axial iodine atom at C-23 and its already reported 23S-epimer. The same treatment of sarsasapogenin acetate led to a single diasteromer characterized as 23S-iodosarsasapogenin acetate. A full characterization of the obtained compound...
A detailed analysis of the course of the reaction of steroid sapogenins with NaNO 2 and BF 3 ·Et 2 O in acetic acid is presented and some evidences on the involved mechanism are provided. Two new products of the studied reaction were isolated and unambiguously characterized with the aid of NMR and single crystal X-ray diffraction.
The full assignments of the 1 H and 13 C NMR signals of steroids bearing the 16β,23:23,26-diepoxy side chain are provided. Differentiation of the diasterotopic H-26 pair was achieved with the aid of NOESY experiments. The main substituent and steric effects associated with this moiety and their influence on the chemical shifts of the neighboring atoms are discussed.
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