Palladium-catalyzed hydroformylation of methyl esters of N-Boc-L-tyros
ine triflate (1a) and N-Boc-4-iodo-L-phenylalanine (1b) followed by re
duction with sodium borohydride and standard deprotection procedures a
ffords the title compound in 77 and 83% overall yield, respectively.