Hydroboration–Suzuki cross coupling of unsaturated amino acids; the synthesis of pyrimine derivatives

Hydroboration of protected allylglycines with 9-BBN followed by Suzuki cross coupling of the resulting organoboranes proceeded smoothly giving a range of new bis-homophenylalanine and related derivatives in good yields (9 examples, 53–64%). One of the Suzuki coupling products has been elaborated to give the N-Cbz-protected natural product pyrimine. The hydroboration–Suzuki coupling of vinylglycine derivatives was also studied but was less efficient than with the allylglycine derivatives: the best results were obtained using disiamylborane·DMS as the hydroborating agent.