Synthesis and preliminary odour evaluation of 5α-androst-16-en-7-one: a new androstenone analogue

5α-Androst-16-en-3-one has been prepared from 5α-androstane-7,17-dione in a five-step sequence, via selective ketalisation at C-7 with bis-trimethylsilyloxyethane and trimethylsilyl triflate as the key step, followed by introduction of the Δ16 bond by reaction of the 17-hydrazone with iodine to give the vinyl iodide, and deiodination with sodium in ethanol, with acid-catalysed deprotection of the 7-oxo group as the final step. The compound has a mild sandalwood odour.