ABSTRACT: The title compound, C(14)H(19)NO(5)S, was prepared by nucleophilic addition of the lithium derivative of methyl-phenyl-sulfone to (3S,4R)-3,4-isopropyl-idene-dioxy-pyrroline 1-oxide. There are four mol-ecules in the asymmetric unit. The crystal structure determination confirms the configuration of the chiral centres as 2R,3S,4R. In the crystal, pairs of O-H?N hydrogen bonds link the mol-ecules into dimers.
Project description:The title compound, C20H26O6, is chiral and crystallizes as a racemate: the relative configuration of the stereogenic centres is 1R*,2R*,3S*,4R*. The cyclo-hexane ring has a chair conformation. The ethyl fragment of the eth-oxy-carbonyl group in the 3-position is disordered over two sets of sites in a 0.650?(6):0.350?(6) ratio. The hy-droxy group acts as a bifurcated hydrogen-bond donor, forming both intra- and inter-molecular hydrogen bonds with ester carbonyl O atoms. The inter-molecular hydrogen bonds form inversion dimers in the crystal.
Project description:N-Fmoc-(2S,3S,4R)-3,4-dimethylglutamine (6) was synthesized from tert-butyl N-Boc-(2S,3S,4R)-dimethylpyroglutamate (13). This synthesis involved selective deprotection of a Boc group from a lactam nitrogen in the presence of a tert-butyl ester, Fmoc protection of the lactam, and a lanthanide-catalyzed transamidation reaction of the Fmoc-protected lactam, using ammonia and dimethylaluminum chloride. The scope of Lewis acid-catalyzed transamidation of acylated lactams was explored through the variation of lanthanide, lactam, acyl group, amine, and aluminum reagent. The reactivity of various metal triflates was found to vary in the following qualitative order: Yb approximately Sc > Er approximately Eu approximately Sm > Ce approximately Ag(I) > Cu(II) approximately Zn. Intriguingly, catalysis was only observed when ammonia was the nitrogen nucleophile; addition of other amidoaluminum complexes to acyl lactams was found to be insensitive to the addition of lanthanides.
Project description:The title compound, C14H20FNO3S, contains two chiral carbon centres and the absolute configuration has been confirmed as (2R,3S). In the crystal, adjacent mol-ecules are linked by weak C-H?O hydrogen bonds, generating zigzag chains along the a-axis direction.
Project description:The title compound, C(14)H(17)NO(5)S, was prepared by oxidation of (2R,3S,4R)-2-phenyl-sulfonyl-methyl-1-hy-droxy-3,4-iso-pro-pyl-idene-dioxy-pyrrolidine. Its crystal structure confirms unequivocally its configuration. Two inter-molecular C-H?O inter-actions help to establish the packing.
Project description:In the title compound, C(11)H(19)NO(5), the five-membered pyrrolidine ring adopts an envelope conformation. The dihedral angles between the carboxyl group plane, the pyrrolidine ring and the meth-oxy group are 59.50?(3) and 62.02?(1)°, respectively. In the crystal, inter-molecular O-H?O hydrogen bonds link the mol-ecules into chains along . The absolute configuration is assigned in accord with that of (2R,4R)-1-(tert-but-oxy-carbon-yl)-4-hy-droxy-pyrrolidine-2-carb-oxy-lic acid, which was the starting material in the synthesis.
Project description:In the title compound, C23H38O5, the oxabicyclo-[2.2.1]heptane-2,3-dicarb-oxy-lic anhydride unit has a normal geometry and the tetra-decoxymethyl side chain is fully extended. In the crystal, mol-ecules are linked head-to-head by C-H?O hydrogen bonds, forming two-dimensional networks propagating along the a and c-axis directions.
Project description:The title compound, C20H42O3S2Si, crystallized with two independent mol-ecules (A and B) in the asymmetric unit. They consist of syn,anti,anti-stereo-tetrads with a 1,3-di-thiane motif and a primary alcohol protected as the triisopropyl silyl ether. The 1,3-di-thiane ring adopts a chair conformation, while the rest of each mol-ecule displays a common zigzag conformation. There is an intra-molecular O-H?O hydrogen bond in each mol-ecule. In the crystal, the A and B mol-ecules are linked via O-H?O hydrogen bonds, forming -A-B-A--B-- chains along . The absolute structure was determined by resonant scattering (anomalous scattering) [Flack parameter = 0.035?(8)].
Project description:The title compound C(7)H(11)NO(3) was prepared by intra-molecular nucleophilic displacement of 2,3-O-iso-propyl-idene-d-erythronolactol. There are two mol-ecules in the asymmetric unit, which are related by a pseudo-inversion centre. The crystal structure determination confirms unequivocally the configuration of the chiral centres as 3S,4R. In the crystal structure, inter-molecular C-H?O inter-actions link the mol-ecules (into infinite zigzag chains along the a axis.
Project description:The crystal structures of (3S,4aS,8aS)-2-[(2R,3S)-3-benzamido-2-benzo-yloxy-4-phenyl-but-yl]-N-tert-butyldeca-hydro-iso-quinoline-3-carboxamide, C38H47N3O4, (I), and (3S,4aS,8aS)-2-[(2R,3S)-3-(2,5-di-chloro-benzamido)-2-(2,5-di-chloro-benzo-yloxy)-4-phenyl-but-yl]-N-tert-butyldeca-hydro-iso-quinoline-3-carboxamide, C38H43Cl4N3O4, (II), are described. Despite their chemical similarity, they adopt different conformations in the solid state: (I) features a bifurcated intra-molecular N-H?(N,O) hydrogen bond from the tert-butylamide NH group to the piperidine N atom and the benzoate O atom, whereas (II) has an intra-molecular N-H?O link from the benzamide NH group to the tert-butyl-amide O atom. In the crystal of (I), mol-ecules are linked by C(4) amide N-H?O hydrogen bonds into chains propagating in the  direction, with both donor and acceptor parts of the benzamide group. In the extended structure of (II), C(11) N-H?O chains propagating in the  direction arise, with the donor being the tert-butylamide NH group and the acceptor being the O atom of the benzamide group.
Project description:A new polymorph of (2S,3S)-2-amino-3-methyl-penta-noic acid, l-isoleucine C6H13NO2, crystallizes in the monoclinic space group P21 with four independent mol-ecules in the asymmetric unit. The mol-ecules are zwitterions. In the crystal, N-H?O hydrogen bonds link two pairs of independent mol-ecules and their symmetry-related counterparts to form two types of layers stacked in an anti-parallel manner parallel to (001). The hydro-phobic aliphatic isopropyl groups protrude from these layers.