Collect. Czech. Chem. Commun.
2011, 76, 443-456
https://doi.org/10.1135/cccc2010145
Published online 2011-04-14 13:32:19
The introduction of a double bond on the steroid skeleton – The preparation of enol silyl ether derivatives from vicinal diols
Aleš Marek, Blanka Klepetářová and Tomáš Elbert*
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám. 2, 166 10 Prague 6, Czech Republic
Abstract
The ways of converting steroid vicinal diol into an unsaturated derivative were studied with the intention of preparing suitable precursors for the introduction of deuterium or tritium into the molecules of brassinosteroids. The model vicinal diol compound, 2α,3α-dihydroxy-5α-pregnane-6,20-dione (3), was converted with high regioselectivity to the α-hydroxy ketone derivative, 2α-hydroxy-5α-pregnane-3,6,20-trione (8), in a 75% yield. The attempts to convert α-hydroxy ketone 8 to the dioxolene derivative, 2α,3α-(isopropylidenedioxy)-5α-pregn-2-ene-6,20-dione (6), failed. The conditions for the conversion of ketone to the corresponding enol trialkylsilyl ether were optimized using cyclohexanone as a model compound. The best and reproducible results were obtained by using tert-butyldimethylsilyl trifluoromethansulfonate (TBDMSiOTf) as the silylating reagent and triethylamine as the base. Under these conditions, the 3,6,20-trione (8) was converted to 2,3-bis(tert-butyldimethylsilyloxy)-5α-pregn-2-ene-6,20-dione (14) with a 66% yield.
Keywords: Enol silyl ether; Vicinal diol; Steroids; Brassinosteroids; X-Ray diffraction.
References: 13 live references.
