Search for "unnatural amino acids" in Full Text gives 28 result(s) in Beilstein Journal of Organic Chemistry.
Beilstein J. Org. Chem. 2012, 8, 640–649, doi:10.3762/bjoc.8.71
Beilstein J. Org. Chem. 2009, 5, No. 81, doi:10.3762/bjoc.5.81
Beilstein J. Org. Chem. 2009, 5, No. 5, doi:10.3762/bjoc.5.5