- Toward the development of a structurally novel class of chiral auxiliaries: Diastereoselective Aldol reactions of a (1R,2S)-ephedrine-based 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one
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(equation Presented) 8 examples Asymmetric aldol addition reactions have been conducted with (1R,2S)-ephedrine-derived 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-one (2). Diastereoselectivities range from 75:25 to 99:1 for the formation of the crude non-Evan
- Casper, David M.,Burgeson, James R.,Esken, Joel M.,Ferrence, Gregory M.,Hitchcock, Shawn R.
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p. 3739 - 3742
(2007/10/03)
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- X-ray crystallographic and proton nuclear magnetic resonance studies of β-hydroxy-N-nitrosamines derived from α-amino acids and ephedrine
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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
- Hitchcock, Shawn R.,Nora, George P.,Hedberg, Christine,Casper, David M.,Buchanan, Laura S.,Squire, Michael D.,West, Douglas X.
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p. 8799 - 8807
(2007/10/03)
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- Biosynthesis of porphyrins and related macrocycles. Part 52.1'2 Synthesis of 1-SH11-4Hjporphobilinogen and the (11R)enantiomer for stereochemical studies on hydroxymethylbilane synthase (porphobilinogen deaminase)
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A synthetic route is devised for the synthesis of (115)-[11-2H,]porphobilinogen la and of the (1 lβ)-enantiomer Ib. Their absolute configurations and enantiomeric purity are established by degradation to a derivative of [2-2H,]glycine of known stereochemistry. Methods are then developed, based on the synthesis of chiral imidate esters, for determination of the configuration of [2H1]-labelled aminomethylpyrroles by converting them into [2H,]-labelled amidines followed by analysis using 'H-NMR. The labelled samples of PEG la and Ib serve as substrates for hydroxymethylbilane synthase and the products are trapped as [2H1]-labelIed aminomethylbilanes 7c and 7d. Their configurations are determined by the NMR assay to demonstrate that as PBG 1 is enzymically converted into the aminomethylbilane 7, there is overall retention of configuration at the aminomethyl carbon. The Royal Society of Chemistry 1999.
- Neidhart, Werner L.,Anderson, Paul C.,Hart, Graham J.,Battersby, Alan R.
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p. 2677 - 2689
(2007/10/03)
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- N-NITROSATION OF SECONDARY AMINES EFFECTED BY ELECTROCHEMICAL OXIDATION OF NITRITE ION IN WEAKLY BASIC MEDIA
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Constant current electrolysis of sodium nitrite in aqueous acetonitrile containing secondary amines at ambient temperature resulted in the formation of the corresponding N-nitrosamines in good yields.KEYWORDS - N-nirosation; secondary amine; sodium nitrite; electrochemical oxidation; constant current electrolysis
- Masui, Masaichiro,Yamawaki, Norihiko,Ohmori, Hidenobu
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p. 459 - 461
(2007/10/02)
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