Diamino-cyclobutene-diones

Diamino-cyclobutene-diones as a-amino carboxylic acid surrogates Diamino-cyclobutene-dione was proposed by Kinney et al e m original surrogate of the a-amino carboxylic acid function (Figure 15.25). 

Diamino-cyclobutene-dione, was proposed by Kirmey et al as an original surrogate of the a-amino carboxyUc acid function (Fig. 13.12). 

In a different approach to carboxylate coniplexation, squaramide (i.e., 3,4-diamino-cyclobutene-1,2-dione) derivatives have been used by Prohens et al. as selective receptors (Fig. Ih). These receptors possess a parallel ditopic hydrogen bond donor array (c.f. urea) that show good to moderate association constants with acetate anions. A variety of mono-, di-. and tritopic receptors were synthesized, including the -squaramide receptor 19 that forms strong complexes with m-carboxylates such as trimesoate and cfs-cyclohexentricarboxylate (i a=3.9 X 1(PM and 7.7 x 10 M . respectively, in 10% DoO/DMSO.)... 

Figure 11.11. 3,4-Diamino-3-cyclobutene-l,2-diones redrawn from Ref. 34.

Many NMDA receptor antagonists have been synthesized that are based on the structure of glutamate, NMDA, and AMPA. Several 3,4-diamino-3-cyclobutene-l,2-dione derivatives (34) have been synthesized and found to be good inhibitors of the NMDA receptor (Fig. 

Kinney, W. A., Lee, N. E., Garrison, D. T, Podlesny, E. J., Jr, Simmonds, J. T, Bramlet, D., Notvest, R. R., Kowal, D. M., Tasse, R. P. Bioisosteric replacement of the a-amino carboxylic functionality in 2-amino-5-phosphonopentanoic acid yields unique 3,4-diamino-3-cyclobutene-l,2-dione containing NMDA antagonists. J. Med. Chem. 1992, 35, 4720-4726. 

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