We have previously reported an aminoacyl-transfer reaction within a stem-overhang RNA structure (Fig. ). Starting from a chemically synthesised aminoacyl-phosphate mixed anhydride at the 5'-terminus of an RNA strand, in combination with a longer overhanging complementary RNA, the aminoacyl-residue is spontaneously transferred to the 3'-terminus forming a 2'/3'-aminoacyl-ester. This mechanism has clear parallels to that of extant biology which utilises an aminoacyl-adenylate mixed anhydride and aminoacyl tRNA synthetases to build 2'/3'-aminoacyl-ester tRNAs. We have also reported recently how the transfer varies with RNA sequence and different amino acids and the possible consequences for the origin of the genetic code. We were interested to see if further equivalents of mixed anhydride would allow subsequent aminoacyl transfer to the aminoacyl-ester amino group to give a 2'/3'-dipeptidyl-ester.