Omura K, Ohsaki A, Zhou B, Kushida M, Mitsuma T, Kobayashi A, Hagey LR, Hofmann AF, Iida T. Improved chemical synthesis, X-ray crystallographic analysis, and NMR characterization of (22R)-/(22S)-hydroxy epimers of bile acids.
Lipids 2014;
49:1169-80. [PMID:
25319478 DOI:
10.1007/s11745-014-3955-y]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 09/11/2014] [Indexed: 11/29/2022]
Abstract
We report an improved synthesis of the (22R)- and (22S)-epimers of 3α,7α,12α,22-tetrahydroxy-5β-cholan-24-oic acid and 3α,7α,22-trihydroxy-5β-cholan-24-oic acid from cholic acid (CA) and chenodeoxycholic acid (CDCA), respectively. The principal reactions involved were as follows: (1) oxidative decarboxylation of the bile acid peracetates with lead tetraacetate, and (2) subsequent Reformatsky reaction of the 23,24-dinor-22-aldehydes with ethyl bromoacetate in the presence of activated Zn as a catalyst with the reaction temperature maintained precisely at 75 °C. The absolute configuration of the chiral center at C-22 of each epimer was established by single-crystal X-ray diffraction data using its ethyl ester-peracetate derivative. The (1)H- and (13)C-NMR spectra that permit the (22R)- and (22S)-epimers to be distinguished are reported as well as the specific (1)H shift effects induced by C(5)D(5)N. Bile acids having hydroxyl groups at C-22 are present in a variety of animal biles, previously have been difficult to identify, and are known to have distinctive physicochemical and biological properties.
Collapse