From the Ene Reaction of Nitrosocarbonyl Intermediates with 3-Methylbut-2-en-1-ol, a New Class of Purine N,O-Nucleoside Analogues

Sterically encumbered nitrosocarbonyl derivatives of mesitylene or anthracene undergo ene reactions with 3-methylbut-2-en-1-ol to give the corresponding the 5-hydroxyisoxazolidine adducts in fair yields. According to the proposed mechanism, these heterocycles are derived from the anti-Markovnikov orientation of the ene reaction. The isoxazolidin-5-yl acetate derivatives are synthons of choice for the preparation of N,O-nucleoside analogues containing purine rings by means of the Vorbruggen protocol.