The principles and practice of solid-phase organic synthesis and combinatorial chemistry are utilized in a laboratory preparation of oligopeptides. A parallel synthesis scheme is used to generate a series of tripeptides. A divergent synthesis scheme is used to prepare two pentapeptides, one of which is leucine enkephalin, a neurotransmitter known to be an analgesic agent.
The basicities of a series of 2,3-disubstituted quinoxalines were determined by potentiometric titration in acetic anhydride. A decrease in basicity was observed for those compounds containing a fused, strained ring adjacent to the heteroatoms. Such an effect was consistent with previous interpretations based on orbital rehybridization. In conjunction with the present study, J (13C-H) values were determined for the benzylic protons of acenaphthene and pyracene.
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