Intramolecular nitrone cyclo-addition

In a similar study the intramolecular nitrone cyclo-addition (INC) reaction at the off-template site afforded several isoxazoUdine-fused saccharides (93 to 98) ° (Scheme 22.22). 

According to general (or principal) Scheme 2.211b, intramolecular 1,3-cyclo-additions of nitrones derived from 3-oxa-6-heptenals (461) and (462) proceed stereoselectively, leading to cycloadducts (463-465) (Scheme 2.223) and (466-468) (Scheme 2.224) in good yields (720). 

Nitrile oxide J -I- 2 cycloaddition.1 A key step in a recent stereospecific synthesis of biotin (6) from cycloheptene (1) is an intramolecular [3 + 2]cyclo-addition of a nitrile oxide (a), obtained by dehydration of a primary nitro compound (3), preferably with phenyl isocyanate. This cycloaddilion is more efficient than the well-known olefinic nitrone cycloaddition. The carbon atoms in 6 derived from cycloheptene are marked with asterisks. 

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See also in sourсe #XX -- [ ]

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