A series of organic diamine base compounds derived from either an aromatic, alicyclic or heterocyclic ring and possessing, for the most part, an intervening methylene group between the ring and the aforesaid basic moiety have been prepared, including their pharmaceutically acceptable acid addition salts as well as oral pharmaceutical compositions containing same. These particular compounds are found to be useful in therapy as oral hypoglycemic agents. Preferred member compounds include 1,1'-[1,2-phenylenebis(methylene)]bispiperidine, 2,3-dihydro-2-[2-(1-piperidinomethyl)phenylmethyl]-1H-isoindole and 2,3-dihydro-2-[2-(4-morpholinomethyl)phenylmethyl]-1H-isoindole. Alternate methods of preparation are provided and the two principal synthetic routes leading to these compounds are described in some detail.