Development of two diastereoselective routes towards trans-4-aminomethyl-piperidin-3-ol building blocks

Two diastereoselective, scaleable routes towards trans-3,4-disubstituted piperidines with a 4-hydroxymethyl-3-hydroxy or 4-aminomethyl-3-hydroxy substitution pattern are being described. In the first route, the 3,4-trans configuration was introduced regio- and diastereoselectively via a hydroboration/oxidation sequence starting from 4-hydroxymethylpyridine. In the second route, regioselective epoxide ring opening of N-benzyl-3,4-epoxy-piperidine was achieved with LiCN, in situ generated from acetocyanohydrin and LiNH2. The regioselectivity of both the hydroboration and the epoxide ring opening was positively influenced by the presence of the basic piperidine nitrogen. Both routes have been optimized to be performed at large scale.