1.Vibrational absorption and circular dichroism studies of (-)-camphanic acid.
Buffeteau T1, Cavagnat D, Bouchet A, Brotin T. J Phys Chem A. 2007 Feb 15;111(6):1045-51. Epub 2007 Jan 24.
Vibrational absorption and circular dichroism (VCD) spectra of (-)-(1S,3R)-camphanic acid have been measured in deuterated chloroform solutions at different concentrations (0.005, 0.045, and 0.200 M) in the mid-infrared spectral range. Experimental spectra have been compared with the density functional theory (DFT) absorption and VCD spectra, calculated using the B3PW91 functional and cc-pVTZ basis set for three conformers of both the monomer and the dimer forms of (-)-(1S,3R)-camphanic acid. These calculations indicate that, in the dilute solution, the conformer with intramolecular hydrogen-bonding between the hydroxyl and lactone groups is of lowest energy and represents 70% of the different monomer conformers at room temperature, whereas, in concentrated solution, the dimer formed by intermolecular hydrogen-bonding of carboxyl groups of the two distinct monomer conformations is stabilized. The vibrational absorption and circular dichroism spectra calculated from the Boltzmann population of the individual monomer and dimer conformers are in very good overall agreement with the corresponding experimental spectra, allowing the absolute conformation and configuration of (-)-(1S,3R)-camphanic acid in dilute and concentrated solution, respectively.
2.Asymmetric Diels-Alder reactions of unsaturated beta-ketoesters catalyzed by chiral ruthenium PNNP complexes.
Schotes C1, Mezzetti A. J Am Chem Soc. 2010 Mar 24;132(11):3652-3. doi: 10.1021/ja910039e.
Cyclic alpha-unsaturated beta-ketoesters undergo cycloaddition with di- and trisubstituted butadienes to give tetrahydro-1-indanone derivatives with up to 93% ee in the presence of a ruthenium catalyst formed by activation of [RuCl(2)(PNNP)] with (Et(3)O)PF(6) (2 equiv) (PNNP = (1S,2S)-N,N'-bis[o-(diphenylphosphino)benzylidene]cyclohexane-1,2-diamine). The protocol has been used to prepare the estrone derivative (8R,13S,14S)-13-tert-butoxycarbonyl-3-methoxy-7,8,12,13,15,16-hexahydro-6H-cyclopenta[a]phenanthren-17(14H)-one as a single diastereoisomer with 85% yield and 99% ee after one crystallization step. Its absolute configuration, which has been determined by X-ray diffraction after reduction to the alcohol and esterification with camphanic chloride, is in agreement with the attack of the diene onto the open enantioface of the beta-keto ester (O-O) in the ruthenium complex [Ru(O-O)(PNNP)](2+), whose X-ray structure has been determined.
3.2-Ethyl-8-methoxy-methyl-4-oxo-4H-chromen-7-yl (1S,4R)-4,7,7-trimethyl-3-oxo-2-oxabicyclo-[2.2.1]heptane-1-carboxyl-ate.
Qiu Y1, Chen Y, Xia P. Acta Crystallogr Sect E Struct Rep Online. 2010 May 26;66(Pt 6):o1459. doi: 10.1107/S1600536810018921.
The title compound C(23)H(26)O(7), was prepared by esterification of 2-ethyl-7-hydr-oxy-8-methoxy-methyl-4H-chromen-4-one with (S)-(-)-camphanic chloride. The two rings of the chromone system are coplanar, making a dihedral angle of 1.99 (19)°, and the camphanoyl unit substituted at 7-O retains the original bicyclo-[2.2.1]heptane conformation of the starting reagent.
4.Antitumor agents. 172. Synthesis and biological evaluation of novel deacetamidothiocolchicin-7-ols and ester analogs as antitubulin agents.
Shi Q1, Verdier-Pinard P, Brossi A, Hamel E, McPhail AT, Lee KH. J Med Chem. 1997 Mar 14;40(6):961-6.
A series of novel 7-O-substituted deacetamidothiocolchicine derivatives has been synthesized and evaluated for their inhibitory activity against tubulin polymerization, the binding of [3H]-colchicine to tubulin, and the growth of human Burkitt lymphoma cells. Of these new derivatives, thiocolchicone (8), wherein an acetamido group in thiocolchicine is replaced by a carbonyl oxygen at C(7), was obtained from deacetythiocolchicine (6) by Schiffs base equilibration and acid hydrolysis. Reduction of thiocolchiocone with sodium borohydride yielded the racemic alcohol 9, the structure of which was verified by X-ray crystallographic analysis. Optically pure alcohols 9a,b were obtained by treatment of 9 with the optically pure reagent (1S)-(-)-camphanic chloride followed by chromatographic separation of the camphanate esters and hydrolysis of the diastereomers. X-ray crystallographic analysis established the aS,7S-configuration of 9a. Racemic and optically active esters 11-15, 11a,b, 12a, 14a, and 15a were obtained by esterification of the corresponding alcohols.
