X=Y-ZH systems as potentials 1,3-dipoles. Part 321,2 generation of nitrones from oximes. Tandem Michael addition-1,3-dipolar cycloaddition reactions. Background and class 1 processes
Intermolecular Michael addition of aldoximes and ketoximes to electronegative olefins generates nitrones. The keto nitrones can be trapped in regiospecific intermolecular cycloaddition reactions giving single cycloadducts in good yield. Chemospecific 1:1:1 cycloadducts are obtained from ketoximes, monosubstituted electronegative olefins (Michael acceptor) and N-methylmaleimide (dipolarophile), whilst the chemoselectivity of the corresponding reactions with aldoximes is dependent on the oxime stereochemistry. Z-Aldoximes show high chemospecificity whilst E-aldoximes are much less chemoselective.
Grigg,Heaney,Surendrakumar,Warnock
p. 4477 - 4494
(2007/10/02)
Thio-sugars. Part 10. The Nucleoside from 5-Fluoroacil and 2-Amino-2,3-dideoxy-4-thio-DL-glycero-tetrofuranose and Related Compounds
Another molecular combination of a chloroethylnitrosourea and a pyrimidine antimetabolite (5-fluorouracil) linked through a sugar or sugar-like moiety has been synthesised for biological testing.In this case 2-amino-2,3-dideoxy-4-thio-DL-glycero-tetrofuranose was derived from thiolan-3-one, nitrogen being introduced as azide in preference to the route involving oxime and phthalimide.Some derivatives of 3-amino-3-deoxy-4-thio-DL-erythrofuranose were prepared from trans-4-aminothiolan-3-ol, inverted by way of a fused oxazoline, but although a (5-iodouracil) nucleoside ester was obtained it proved difficult to remove the protecting groups.
Jones, John O.,McElhinney, R. Stanley
p. 1501 - 1517
(2007/10/02)
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