Biomedical Engineering Reference
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SCHEME 3.26
Intramolecular nitrone and nitrile oxide cycloaddition reactions.
and isoxazolidines 81 to 84 (Scheme 3.26) [46]. Intramolecular nitrile oxide (INOC)
and nitrone (INC) cycloaddition reactions were explored. With few exceptions, all
1,3-dipolar cycloadditions proceeded in good yield and with excellent diastereose-
lectivity.
In addition, a suggested mechanism for the intramolecular nitrone cycloaddition
reaction is shown in Figure 3.4. As illustrated in the transition states proposed,
a major steric interaction exists between the oxygen and the benzyl group when
the allylic group approaches the nitrone from the si side. In contrast, the minor
steric interaction between the nitrone oxygen and the hydrogen at position 2 makes
transition state (a) more favorable. The cis orientation at positions 3, 7, and 8 and the
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