Lividamine and paromamine were converted into two key intermediate ethylenic aldehydes 10a and 10b. Reductive amination of the two aldehydes yielded the protected sisamine 11a and the three analogs 11b, 12a and 12b. These four derivatives were deprotected to yield the four pseudodisaccharides 1a, 1b, 2a and 2b which were less active in vitro than neamine against Escherichia coli ATCC 9637 and Staphylococcus aureus 209P.