General Papers ARKIVOC 2000 (i) 80-86
Synthesis and 13C NMR chemical shift assignments of 2,2'bipyridine- 4,4'-dicarboxylates of bile acid methyl esters
Jari T. Tamminen*, Erkki T. Kolehmainen, Mervi H. Haapala, Hannu T. Salo, and Juha
M. Linnanto Department of Chemistry, University of Jyväskylä, P.O. Box 35, FIN-40351, Jyväskylä, Finland E-mail:
[email protected]
(received 15 Dec 99; accepted 13 Feb 00; published on the web 21 Feb 00)
Abstract Novel 2,2'-bipyridine-4,4'-dicarboxylates 3a-3d of four bile acid methyl esters have been synthesized from 2,2'-bipyridine-4,4'-dicarboxylic acid 1 and the corresponding bile acid methyl esters (methyl lithocholate 2a, methyl chenodeoxycholate 2b, methyl deoxycholate 2c, and methyl cholate 2d). In addition to the desired products, 3a -(2,6-dichlorophenylcarboxy) bile acid methyl esters 4a-4d were obtained. The structures of 3a-4d have been ascertained by 1 D 1H and 13C NMR, 2 D PFG 1H,13C HMQC, and MALDI TOF MS. Molecular weights and 13C NMR chemical shifts of 3a-4d have been presented. The geometry of 3a has been optimized semiempirically at the PM3 level and it has been observed that the minimum energy structure of 3a is a open type conformation due to lack of attractive intramolecular electrostatic interactions between the heads of the molecule which would have favoured the formation of cleft type structure. The synthesized bipyridine-bile acid conjugates are interesting structures from the molecular recognition point of view because they could have potential to form complexes with some transition metal ions, for example with silver, cadmium, and ruthenium.
Keywords: Bipyridine-bile acid, methyl lithocholate, methyl chenodeoxycholate
Introduction
Bile acids have shown to be versatile building blocks in tailoring supramolecular hosts.1-7 They also have pharmacological potential to act as carriers of liver-specific drugs, absorption enhancers, and as cholesterol-lowering agents,8 which have made bile acids extensively studied compounds in chemistry and medicine. We have recently reported synthetic procedures for preparing a lithocholaphane9 and steroidal molecular clefts containing three arylcarboxy,10 isomeric pyridine-n-carboxy,11 and isomeric n-acetoxyphenylcarboxy (acetylsalicylate and its isomers)12 moieties and their complexation tendencies towards silver(I)-cation.11 By introducing various heteroatoms, and especially nitrogen containing moieties, into the bile acid derivatives, their coordination spheres for cation binding can be greatly enhanced. From this
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