Upon reaction with an excess of 2,2-dimethylpropane-1,3-diol (neopentyl glycol) under acid catalysis, estrones form 17-O-[2′,2′-dimethyl-2′-(5″,5″-dimethyl-1″,3″-dioxanyl)ethyl] substituted estra-3, 17β-diols. The reaction represents a formal reduction of a keto function under acidic conditions in the absence of a metal.