Browsing by Author "Cordes, David B. (TTU)"
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Item Group-Assisted Purification (GAP) Chemistry for the Synthesis of Velcade via Asymmetric Borylation of N-Phosphinylimines(2014) Xie, Jian Bo (TTU); Luo, Jian (TTU); Winn, Timothy R. (TTU); Cordes, David B. (TTU); Li, Guigen (TTU)A new approach to the anticancer drug Velcade was developed by performing asymmetric borylation of an imine anchored with a chiral N-phosphinyl auxiliary. Throughout the 7-step synthesis, especially in the imine's synthesis and in the asymmetric borylation reactions, operations and work-up were conducted in simple and easy ways without any column chromatographic purification, which defines the GAP (group-assisted purification) chemistry concept. It was found that the optically pure isomer (dr > 99:1) can be readily obtained by washing the crude mixture of the asymmetric borylation reaction with hexane; the chiral N-phosphinyl auxiliary can be easily recovered after deprotection is finished. Several other N-phosphinylimines were also investigated for the asymmetric borylation reaction. The absolute configuration of the borylation product was confirmed by single crystal X-ray diffraction analysis.© 2014 Xie et al.Item Tert-butyl N-(thiophen-2-yl)carbamate(2013) Hsu, Gene C. (TTU); Singer, Laci M. (TTU); Cordes, David B. (TTU); Findlater, Michael (TTU)In the title compound, C9H13NO2S, the dihedral angle between the thiophene ring and the carbamate group is 15.79 (14)°. In the crystal structure, intramolecular C - H⋯O interactions in tandem with the tert-butyl groups render the packing of adjacent molecules in the [001] direction nearly perpendicular [the angle between adjacent thiophene rings is 74.83 (7)°]. An intermolecular N - H⋯O hydrogen bond gives rise to a chain extending along [001]. The crystal studied was found to be a racemic twin. © 2013 Hsu et al.Item Thiophene-2-carbonyl azide(2013) Hsu, Gene C. (TTU); Singer, Laci M. (TTU); Cordes, David B. (TTU); Findlater, Michael (TTU)The title compound, C5H3N3OS, is almost planar (r.m.s. deviation for the ten non-H atoms = 0.018 Å) and forms an extended layer structure in the (100) plane, held together via hydrogen-bonding interactions between adjacent molecules. Of particular note is the occurrence of RC - H⋯N -=N+=NR interactions between an aromatic C - H group and an azide moiety which, in conjunction with a complementary C - H⋯O=C interaction, forms a nine-membered ring.