Cubane tetracarboxylic acid

Other popular scaffolds have been derivatives of biphenyls which are now readily prepared using solid phase methods [265,464-469]. A solution phase approach has been to react a polyfunctional ised core containing reactive groupings - acid chlorides or isocyanates are easily prepared examples -with a mixture of reagents. One of the earliest synthetic examples showed the use of cubane tetracarboxylic acid chloride [151]. Two recent methods have used functionalised xanthene (library 71) [470] or diphenylmethane cores (library 72) [471] to identify DNA and urokinase receptor antagonists respectively. 

R. J. Butcher, A. Bashir-Hashemi, R. Gilardi, Network hydrogen bonding the crystal and molecular structure of cubane-l,35,7-tetracarboxylic acid dihydrate , J. Chem. Cryst., 1997, 27, 99-107. 

Eaton and co-workers also reported the synthesis of 1,3,5-trinitrocubane and 1,3,5,7-tetranitrocubane (39) ° The required tri- and tetra-substituted cubane precursors were initially prepared via stepwise substitution of the cubane core using amide functionality to permit ort/jo-lithiation of adjacent positions. The synthesis of precursors like cubane-1,3,5,7-tetracarboxylic acid was long and inefficient by this method and required the synthesis of toxic organomercury intermediates. Bashir-Hashemi reported an ingenious route to cubane-1,3,5,7-tetracarboxylic acid chloride (35) involving photochemical chlorocarbonylation of cubane carboxylic acid chloride (34) with a mercury lamp and excess oxalyl chloride. Under optimum conditions this reaction is reported to give a 70 8 22 isomeric mixture of 35 36 37... 

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