Successful prediction of the hydrogen bond network of the 3-oxo-12alpha-hydroxy-5beta-cholan-24-oic acid crystal from resolution of the crystal structure of deoxycholic acid and its three 3,12-dihydroxy epimers

Ice-like encapsulated water by two cholic acid moieties

Starting from the structure of ice (in which each water molecule is surrounded by other four water molecules forming a tetrahedron with a value of 4.51Å for the edge O-O distance), and the knowledge that this value also corresponds to the O7-O12 distance of the skeleton of cholic acid, it is hypothesized that two steroid cholic acid moieties, with an appropriate steroid-steroid distance and a belly-to-belly orientation, could encapsulate a single water molecule between them. To check this hypothesis two succinyl derivatives of cholic acid (a monomer and the related head-head dimer in which the succinyl group is the linking bridge) were designed. The expected "ice-like" structure is found in the crystal of the dimer. There is a hydrogen bond synergy between those participating in the "ice-like" structure, and those in which the bridge is involved with the O7-H hydroxy group and the side chain of the steroid.

Formation of tubules by p-tert-butylphenylamide derivatives of chenodeoxycholic and ursodeoxycholic acids in aqueous solution

The formation of tubules by p-tert-butylphenylamide derivatives of chenodeoxycholic and ursodeoxycholic acids in aqueous solution is investigated. The critical aggregation concentrations of the new surfactants are much lower than those of ursodeoxycholate and chenodeoxycholate, indicating the enhanced surfactant properties resulting by the presence of the hydrophobic p-tert-butylphenyl group. The molecular areas at the air-water interface suggest the formation of monolayer films with molecules upright oriented. The shape of the aggregates was investigated by TEM. The main structure present in solution corresponds to tubules. The estimated value for the wall thickness of tubules suggests that a bilayer structure is formed. Host of positively charged latex beads by tubules suggests that their inner and outer surfaces are negatively charged. The acid form of the chenodeoxycholate derivative was recrystallized from toluene and its crystal structure analyzed.

Isolation and X-ray Structure of Deoxycholic Acid from the Sponge Ircinia sp

Ethyl acetate extract of the sponge Ircinia sp., collected by SCUBA divers off the coast of southern India, contained a cholest-based sterol of insignificant antimicrobial activity, with one carboxylic acid side chain (3α, 7β-dihydroxy-5β-cholan-24-oic acid, DCA). The structure of the compound was determined by spectroscopic data and single crystal X-ray diffraction studies. DCA crystallizes in the tetragonal space group P41212, chirality documented by solution optical rotation [α]D = +67.4° ( c 0.16, CHCl3).

Supramolecular structures generated by a p-tert-butylphenylamide derivative of deoxycholic acid. From planar sheets to tubular structures through helical ribbons

The formation of supramolecular structures initiated by a p-tert-butylphenylamide derivative of deoxycholic acid (Na-t-butPhDC) is investigated. At 1.18 mM concentration of Na-t-butPhDC and 37 degrees C, initial flat ribbons are observed which self-transform into helical ribbons (with a mean pitch angle of 47 +/- 6 degrees) which finally originate molecular tubes with an external diameter of 241 +/- 28 nm. Most of the molecular tubes show helical markings with a pitch angle value of 45 +/- 4 degrees, in full agreement with predictions of simple models based on chiral elastic properties of the membrane. A lateral association mechanism is proposed to account for the growth of the external diameter (from 225 +/- 32 to 546 +/- 59 nm) of tubes with time at 3.99 mM.

Influence of the solvent ability to form hydrogen bonds in the crystal structure of ([3beta,5beta,7alpha,12alpha]-3[(norbornyl-2-acetyl)-amino]-7,12-dihydroxycholan-24-oic acid (a norbornyl derivative of cholic acid)

A norbornyl-2-acetyl derivative of cholic acid ([3beta,5beta,7alpha,12alpha]-3[(norbornyl-2-acetyl)-amino]-7,12-dihydroxycholan-24-oic acid -NbCH2CA-) was synthesized and recrystallized in two dipolar aprotic solvents (acetone, DMSO) and in one protic solvent (2-propanol). In DMSO and acetone the crystals are orthorhombic, P2(1)2(1)2(1) (all their parameters being very similar) while in 2-propanol the crystal is monoclinic, P2(1). The inclusion complexes with the solvent have a 1:1 stochiometry with DMSO and acetone and 1:2 with 2-propanol. All solvents are forming a hydrogen bond with the amide bond of the bridge between the norbornyl residue and the steroid nucleus of the bile acid. In DMSO and acetone the beta side of the steroid groups lies in the same region facilitating hydrophobic interactions, and the molecules are disposed in an antiparallel orientation (the methyl groups having a beta interdigitation) forming bilayers. The width of the bilayers is 9.231 A and 8.859 A in DMSO and acetone, respectively. A lamellar structure is also evident for the crystal in 2-propanol (the width being 11.908 A), but the packing is different from the previous one since a sliding between the steroid groups is observed and the methyl groups are not interdigitated. Four different hydrogen bonds are established by every steroid molecule in the NbCH2CA/DMSO (or acetone) crystal. This hydrogen bond network interconnects the hydrophilic regions of the lamellar structure. The hydrogen bond network of the NbCH2CA:2-propanol crystal is different because of the different abilities of 2-propanol to form hydrogen bonds. The side chain has a ttti conformation in the two orthorhombic crystals, and a tgtg one in the monoclinic crystal.

Crystal structure of chenodeoxycholic acid, ursodeoxycholic acid and their two 3beta,7alpha- and 3beta,7beta-dihydroxy epimers

The crystal structures of chenodeoxycholic acid (CDCA), ursodeoxycholic acid (7beta isomer of CDCA) and their other two epimers (3beta,7alpha- and 3beta,7beta-isomers) have been resolved. The four isomers were recrystallized from p-xylene. CDCA crystal is hexagonal P6(5) while the crystals of the other three isomers are orthorhombic (P2(1)2(1)2(1) space group). Only the 3beta,7beta isomer forms an inclusion complex with the solvent with a 1:1 stoichiometry. In all cases, the three hydrogen bond sites (the two hydroxy groups, O3-H and O7-H, and the carboxylic acid group of the side chain, O24bO24a-H) simultaneously act as hydrogen bond donors and acceptors. By considering that O24a is always donor and O24b is always acceptor, the hydrogen bond sequences can be understood on the basis of the interaction between the two hydroxy groups. However the comparison between the four compounds is complicated by the existence of two molecules in the asymmetric unit in the UDCA crystal resulting in that the same hydrogen bond site (for instance O3) can be donor towards two different acceptors (either O7 or O24b). As in the case of the four isomers of deoxycholic acid (Steroids 2004, 69, 379), the other three isomers present a donor-->acceptor sequence, which is O7-->O3 when O3-H is beta and O3-->O7 when O3-H is alpha. The spatial orientation of the carboxylic acid of the side chain is referred to two almost perpendicular planes (defined by (1) the carbon atoms C1/C6-C17/C20 and by (2) the methyl groups C18-C19 and the two carbon atoms to which they are linked, C10 and C13, respectively). Only the side chain of CDCA evidences a positive deviation towards the hydrophobic beta side of the molecule.

Steroids: partial synthesis in medicinal chemistry

This article reviews the progress in the chemistry of the steroids that was published between January and December 2004. The reactions and partial synthesis of estrogens, androgens, pregnanes, cholic acid derivatives, cholestanes and vitamin D analogues are covered. There are 127 references.