We describe a general approach, based on the palladium-catalysed coupling of enynes with vinyl triflates, for the construction of dienynes related to vitamin D metabolites and analogues. As an application of this method, an efficient convergent synthesis of 1α, 25- dihydroxyvitamin D3 starting from the Inhoffen-Lythgoe diol (6a) and natural carvones has been carried out (11 steps, 28% overall yield from 6a). This strategy allows labelling of the ...