Aminoalcohol ring cleavage

Aminoalcohol Ring Cleavage of Nitrile Oxide Cycloadducts Synthesis of... 

Aminoalcohol Ring Cleavage of Nitrile Oxide Cycloadducts Synthesis of Amino Polyols, Amino Sugars, and Amino Acids... 

Epoxides may be cleaved by amines. This reaction is used in the synthesis of aminoalcohols (53) studied as potential adrenergic drugs (Scheme 21). The amine cleavage of the epoxide and the subsequent nitrous acid deamination of the aminoalcohol are used for the ring enlargement of alicyclic ketones (TiffeneauDemjanov reaction). By this sequence of reactions, for example, cycloheptanone (54) may be converted to cydooctanone (55) (Scheme 21). 

Attempts to prepare the required bicyclic azetidines by selective reduction of the C-7 carbonyl bond in penicillins failed [66, 67,68] treatment with diborane in THF gave exclusively the aminoalcohols 107 resulting from the cleavage of the four-membered ring (Scheme 34). However, 3-hydroxypropylamine derivatives can be transformed into azetidines, using for instance a modified Mitsonobu reaction [69, 70]. Nevertheless, this transformation was unsuccessful with compound 107b because cyclisation occurred onto the acylamino side-chain to yield dihydrooxazole 108 (Scheme 35). 

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