Highly diastereoselective route to trans-5-substituted 2-hydroxymethylpyrrolidine derivatives by radical cyclisation

The cyclisation of radical species generated from (S)-N-(3-bromopropyl)oxazolin-2-ones 22 by treatment with tributylstannane in the presence of AIBN yielded 5-substituted pyrrolooxazolones with high diastereoselectivity. In the same reaction using (±)-N-(3-bromobutyl)oxazolin-2-one 25a or (±)-N-(4-bromopentan-2-yl)oxazolin-2-one 25b, the radical cyclisation gave predominantly the (5S*,7S*,7aR*)5,7-disubstituted pyrrolooxazolines rather than the (5S*,7R*,7aR*) products. The radical cyclisation of 4-phenylsulfanyloxazolidinones 29a,b also resulted in the predominant formation of the corresponding (5S,7S,7aR)-5,7-disubstituted pyrrolooxazolidine derivatives.