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Merck
  • Rapid conversion of spirostans into furostan skeletons at room temperature.

Rapid conversion of spirostans into furostan skeletons at room temperature.

Steroids (2011-11-09)
Omar Viñas-Bravo, Roxana Martinez-Pascual, José Luis Vega-Baez, Víctor Gómez-Calvario, Jesús Sandoval-Ramírez, Sara Montiel-Smith, Socorro Meza-Reyes, Alejandra López-De Rosas, Mónica Martínez-Montiel, Mayra Reyes, José A Ruiz
ABSTRACT

We report a facile protocol to obtain 22-substituted furostans and pseudosapogenins in high yields from (25R)- and (25S)-sapogenins. This method involves the treatment of the sapogenin with acetic-trifluoroacetic mixed anhydride and BF(3)·OEt(2) at room temperature, followed by the addition of a nucleophile (H(2)O, MeOH or KSeCN). In the case of 22-hydroxyfurostans, they can be transformed to pseudosapogenins by treatment with p-toluensulfonic acid.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Trifluoroacetic anhydride, ReagentPlus®, ≥99%
Supelco
Trifluoroacetic anhydride, derivatization grade (GC derivatization), LiChropur, ≥99.0% (GC)
Sigma-Aldrich
p-Toluenesulfonic acid monohydrate, ReagentPlus®, ≥98%
Sigma-Aldrich
Boron trifluoride diethyl etherate
Sigma-Aldrich
Boron trifluoride diethyl etherate, purified by redistillation, ≥46.5% BF3 basis
Sigma-Aldrich
Silver p-toluenesulfonate, ≥99%
Sigma-Aldrich
p-Toluenesulfonic acid monohydrate, ACS reagent, ≥98.5%
Sigma-Aldrich
Sodium p-toluenesulfonate, 95%
Sigma-Aldrich
p-Toluenesulfonic acid monohydrate, SAJ first grade, ≥99.0%