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1 H, 13 C and 15 N NMR and electrospray ionization time-of-flight mass spectrometric characterizations of five lithocholate esters of piperazine diamides are described. Two of them are cholaphane-type cyclic structures esterified with 2,2 -bipyridine-4,4 -and pyridine-2,6-dicarboxylic acid and the other three esters are open structures comprising two or four lithocholyl residues. The conformational preferences of the dimeric congeners were examined by using molecular modelling and variable-temperature 1 H NMR techniques.

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3α,3′α‐Bis(arylcarboxy)‐5β‐cholan‐24‐oic acid ethane‐1,2‐diol diesters (1–3) were synthesized by the reaction of an aroyl chloride (aroyl=2,6‐dichlorobenzoyl, 2‐naphthoyl and 1‐pyrenoyl) with lithocholic acid (3α‐hydroxy‐5β‐cholan‐24‐oic acid) ethane‐1,2‐diol diester. The 13C NMR chemical shift assignments of the formed molecular clefts 1–3, pyrene‐1‐carboxylic acid methyl ester (4) (used as model compound) and 1‐pyrenoyl chloride (5) are based on literature data and 13C DEPT‐135, 1H,13C HMQC and 1H,13C HMBC experiments. The molecular weights of 1–3 were determined by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. Copyright © 1999 John Wiley & Sons, Ltd.