David M. Casper
Illinois State University
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Featured researches published by David M. Casper.
Tetrahedron-asymmetry | 2003
David M. Casper; Shawn R. Hitchcock
Abstract The direct formation of the titanium enolate of N 3 -propionyl-3,4,5,6-tetrahydro-2 H -1,3,4-oxadiazin-2-one has been achieved through complexation with titanium tetrachloride at 25°C, followed by deprotonation with triethylamine (−78 to 25°C). The preformed titanium enolate has been reacted with D 2 O/DCl to afford deuterated derivative 6 and also reacted with a series of aromatic and aliphatic aldehydes affording aldol adducts 4a – f with crude diastereoselectivities ranging from 8:1 to 38:1.
Tetrahedron | 2001
Shawn R. Hitchcock; George P. Nora; David M. Casper; Michael D. Squire; Christopher D. Maroules; Gregory M. Ferrence; Lisa F. Szczepura; Jean M. Standard
Abstract 3,4,5,6-Tetrahydro-2H-1,3,4-oxadiazin-2-ones derived from (1R,2S)-ephedrine and (1S,2S)-pseudoephedrine have been synthesized and their conformational properties have been examined. The ephedrine heterocycles 5–7a appear to favor one set of equilibrating conformers while the pseudoephedrine heterocycles 5–7b exist as multiple conformers at room temperature. The observed conformational behavior of these heterocycles is attributed to allylic strain and a gauche effect arising from the torsional energy barrier between the lone pair electrons of the N3- and N4-nitrogens.
Tetrahedron | 2000
Shawn R. Hitchcock; George P. Nora; Christine Hedberg; David M. Casper; Laura S. Buchanan; Michael D. Squire; Douglas X. West
Abstract β-Hydroxy-N-nitrosamines derived from l -leucine, l -valine, l -phenylalanine, d -phenylglycine and (1R,2S)-ephedrine have been synthesized and analyzed. These compounds all exhibit rotameric populations of (E)- and (Z)-stereoisomers that are a result of the barrier to rotation about the N-nitroso (N–NO) group. A correlation is made between the X-ray crystallographic data of the N-nitroso-ephedrine derivative 6 and the 1H NMR of the N-nitrosamines 4a–4d. From this comparison, the identities and ratios of (E)- and (Z)-rotamers were unambiguously assigned. Finally, the 1H NMR also provides some insight into the conformational changes that occur when the nitrosamine rotamers interconvert.
Synthetic Communications | 2004
David M. Casper; David Kieser; Jennifer R. Blackburn; Shawn R. Hitchcock
Abstract A series of 3,4,5,6‐tetrahydro‐2H‐1,3,4‐oxadiazin‐2‐ones have been synthesized from valine, leucine, ephedrine, and norephedrine. The synthesis is accomplished through a process of nitrosation, reduction, and cyclization. The cyclization protocol employed involves the use of a metal hydride (LiH or NaH) and diethyl carbonate rather than 1,1′‐carbonyldiimidazole.
Acta Crystallographica Section E-structure Reports Online | 2009
Dishant Tailor; Kate L. Edler; David M. Casper; Shawn R. Hitchcock; Gregory M. Ferrence
The title compound, C16H22N2O3, was synthesized during the course of a study on (1R,2S)-norephedrine-derived 1,3,4-oxadiazinan-2-ones. The conformation adopted by the isopropyl group is pseudo-axial relative to the oxadiazinan core. The allylic strain contributes to this conformational arrangement.
Synthetic Communications | 2007
David M. Casper; Shawn R. Hitchcock
Abstract N‐tert‐Butyldecahydro‐3‐isoquinoline carboxamide (1) is a key structural fragment present in a variety of medicinally important HIV protease inhibitors. Derivatives of this carboxamide were prepared by alkylation with either 2‐iodoethanol, allyl bromide, or bromoacetaldehyde dimethylacetal. The corresponding aldehyde of the dimethylacetal derivative was prepared by reaction with BBr3 in CH2Cl2.
Journal of Organic Chemistry | 2004
Shawn R. Hitchcock; David M. Casper; Jeremy F. Vaughn; Jennifer M. Finefield; Gregory M. Ferrence; Joel M. Esken
Journal of Organic Chemistry | 2002
David M. Casper; Jennifer R. Blackburn; Christopher D. Maroules; Tana Brady; Joel M. Esken; Gregory M. Ferrence; Jean M. Standard; Shawn R. Hitchcock
Journal of Heterocyclic Chemistry | 2002
David M. Casper; George P. Nora; Jennifer R. Blackburn; Jeromy T. Bentley; Deanna C. Taylor; Shawn R. Hitchcock
Journal of Heterocyclic Chemistry | 2008
Shawn R. Hitchcock; Ryan A. Davis; Daniel M. Richmond; Delvis D. Dore; Stephanie L. Kuschel; Jeremy F. Vaughn; Jesse A. Wolfe; Christopher G. Hamaker; David M. Casper; Jarvis Dingle