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I. Structural Analysis Using 15N NMR Spectroscopy II. An Investigation of the Interaction of Grignard Reagents with Mesityl Ketones

Citation

Abe, Amy (1979) I. Structural Analysis Using 15N NMR Spectroscopy II. An Investigation of the Interaction of Grignard Reagents with Mesityl Ketones. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/m0ya-bx45. https://resolver.caltech.edu/CaltechTHESIS:03012018-155039057

Abstract

PART I. Structural Analysis Using 15N NMR Spectroscopy

The proton-coupled, natural-abundance 15N NMR spectra of three series of compounds were examined with emphasis on obtaining conformational, structural and configurational data.

Amino acids and peptides. Chemical shifts of aliphatic amino acids and glycyl dipeptides followed typical α, β, and γ-substituent effects. Vicinal 15Nα, Hβ coupling constants were obtained for seven amino acids and Gly-X dipeptides which possess ~ither a single or three equivalent β-protons. Average vicinal couplings were obtained for amino acids with diastereotopic β-protons. Conformational preferences for the rotamers about the Cα - Cβ bond of threonine and allothreonine were found by extending the traditional Pachler analysis to allow for interaction among substituents through treating both population and torsion angle as variables. Hydrogen-bond formation between the hydroxyl and the carboxylate was favored over that between the hydroxyl and nitrogen for both amino acids.

Biotin. The proton on the N1' nitrogen of biotin exchanges more readily with solvent than that on the sterically-hindered N3' nitrogen. The order of exchange was established through correlation of the nitrogen NMR resonances with the ureido proton resonances by variable single-frequency decoupling of the ureido protons and through assignment of the proton spectrum by homonuclear-decoupling experiments. Assignment of the nitrogen resonances in biotin (N1' = 285.6 ppm and N3' = 294.7 ppm) and desthiobiotin (N1' = 279.3 ppm and N3' = 285.0 ppm) was achieved with the aid of single-frequency, proton-decoupled nitrogen resonances with partial NOE.

Oximes. The large difference between two-bond 15N, Hα coupling constants for the E- and Z-isomers of the oximes allows the configurations of aldoximes to be assigned from geminal couplings obtained from the 15N NMR spectra and also the configuration of O-alkylaldoximes from nitrogen spectra in which the protons on the alkyl group are selectively decoupled.

PART II. An Investigation of the Interaction of Grignard Reagents with Mesityl Ketones

The reaction of acetomesitylene with benzyl Grignard reagent was reinvestigated because of uncertainty in the mechanism and site of addition of the benzyl moiety. The addition product was identified as mesitylmethylbenzylcarbinol as is consistent with a "normal" addition to the ketone proceeding through an initial ketone-Grignard reagent complex.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Unknown, Unknown
Thesis Committee:
  • Ireland, Robert E. (chair)
  • Roberts, John D.
  • Richards, John H.
  • Dervan, Peter B.
  • Dickerson, Richard E.
Defense Date:5 March 1979
Funders:
Funding AgencyGrant Number
Earle C. Anthony FellowshipUNSPECIFIED
NIHUNSPECIFIED
Record Number:CaltechTHESIS:03012018-155039057
Persistent URL:https://resolver.caltech.edu/CaltechTHESIS:03012018-155039057
DOI:10.7907/m0ya-bx45
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10744
Collection:CaltechTHESIS
Deposited By: Melissa Ray
Deposited On:02 Mar 2018 23:35
Last Modified:16 Apr 2021 22:56

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