title: Synthesis of [3,4-(13)c(2)]-enriched bile salts as NMR probes of protein-ligand interactions.
abstract: Synthetic methodology that allows for incorporation of isotopic carbon at the C-3 and C-4 positions of bile salts is reported. Three [3,4-(13)C(2)]-enriched bile salts were synthesized from either deoxycholic or lithocholic acid. The steroid 3alpha-OH group was oxidized and the A-ring was converted into the Delta(4)-3-ketone. The C-24 carboxylic acid was next converted into the carbonate group and selectively reduced to the alcohol in the presence of the A-ring enone. Following protection of the 24-OH group, the Delta(4)-3-ketone was converted into the A-ring enol lactone. Condensation of the enol lactone with [1,2-(13)C(2)]-enriched acetyl chloride and subsequent Robinson annulation afforded a [3,4-(13)C(2)]-enriched Delta(4)-3-ketone that was subsequently converted back into a 3alpha-hydroxy-5beta-reduced bile steroid. C-7 hydroxylation, when necessary, was achieved via conversion of the Delta(4)-3-ketone into the corresponding Delta(4,6)-dien-3-one, epoxidation of the Delta(6)-double bond, and hydrogenolysis/hydrogenation of the 5,6-epoxy enone system. The [3,4-(13)C(2)]-enriched bile salts were subsequently complexed to human ileal bile acid binding protein (I-BABP), and (1)H-(13)C HSQC spectra were recorded to show the utility of the compounds for investigating the interactions of bile acids with I-BABP.
authors.affiliation: Department of Molecular Biology & Pharmacology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8103, St. Louis, Missouri 63110, USA.
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Tochtrop
authors.forename: Gregory T
authors.initials: GT
authors.lastname: DeKoster
authors.forename: David P
authors.initials: DP
authors.lastname: Cistola
authors.forename: Douglas F
authors.initials: DF
authors.lastname: Covey
mesh_terms: D001647:Bile Acids and Salts / Q000138:chemical synthesis* / Q000737:chemistry; D002247:Carbon Isotopes; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D002635:Chenodeoxycholic Acid / Q000737:chemistry*; D002793:Cholic Acids / Q000737:chemistry*; D020650:Combinatorial Chemistry Techniques / Q000379:methods*; D003840:Deoxycholic Acid / Q000737:chemistry*; D006801:Humans; D006913:Hydroxysteroid Dehydrogenases; D007202:Indicators and Reagents; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008562:Membrane Glycoproteins; D015394:Molecular Structure; D013237:Stereoisomerism; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific)
chemical_list: D001647:Bile Acids and Salts; D002247:Carbon Isotopes; D002352:Carrier Proteins; D002635:Chenodeoxycholic Acid; D002793:Cholic Acids; D003840:Deoxycholic Acid; D006913:Hydroxysteroid Dehydrogenases; D007202:Indicators and Reagents; D008024:Ligands; D008562:Membrane Glycoproteins; C037643:bile acid binding proteins; C435496:AKR1C2 protein, human; D045002:3-alpha-Hydroxysteroid Dehydrogenase (B-Specific); C007036:cholanic acid