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Crystal Structure of a Head-to-Head Bis(cholic)-Urea Dimer
1 , 1 , 1 , 1 , 2 , 3 , 1 , * 1
1  Universidad de Santiago de Compostela
2  Escuela de Química, Centro de Investigación en Electroquímica y Energía Química (CELEQ), Universidad de Costa Rica, San José, Costa Rica
3  Dipartimento di Chimica, Università di Roma "Sapienza", P. le A. Moro 5, 00185 Roma, Italy

Abstract: A head-to-head dimer of cholic acid linked at C3 carbon atoms by a urea bridge was synthesized and the crystal structure was studied. The crystal belongs to the monoclinic crystal system, space group I2. The packing shows a bilayer structure with alternating hydrophobic and hydrophilic layers. The horizontal and vertical planes of the two cholic residues are almost parallel to each other, the vertical ones being perpendicular to the bilayers. The hydrogen bond network is two-dimensional as it does not propagate in the direction perpendicular to the bilayers. It is noteworthy that the nitrogen atoms of the urea bridge do not participate in that network. The carbonyl urea group and only one of the ester of the two side chains form hydrogen bonds with two other dimers through the steroid hydroxy O7-H and O12-H groups. This means that each dimer forms eight hydrogen bonds but only four are different.
Keywords: Cholic; bile acid; crystal structure
Comments on this paper
José Vázquez Tato
Typescript error
There is a typescript error in page 3 of the paper:
The acronym  "DEPC" refers to "Diethyl cyanophosphonate" and not to "Diethylpyrocarbonate" as indicated at the manuscript.
Mohamed Moustafa
I can see the acronym DEPC is correctly refers to DIETHYL PYROCARBONATE. You can find a lot of sources using this abbreviation.
for example sigma sell DEPC and its info as follows: product Number D5758 Storage Temperature 2-8°C

CAS #: 1609-47-8
Synonyms: DEPC, DEP, Pyrocarbonic Acid Diethyl ester, Diethyl Oxydiformate, dicarbonic acid diethyl ester6