Azetidine 2-phosphonic acids

Substituted azetidine 2-phosphonic acids 4 were prepared in enantiopure form via N-alkylation of the starting P-amino alcohols with a methylene phosphonate moiety, followed by sequential chlorination and stereoselective 4-exo-tet ring closure <02TL4633>. 

Couty et al. have described an efficient asymmetric synthesis of enantiomerically pure azetidinic 2-phosphonic acids, starting from readily available P-amino alcohols [29],... 

Novel fused systems include the bicyclic phosphonic acid esters (10) (93ZOB1906) and the tricyclic azetidine (11, R = Boc and R = COAr) (93T5047). 

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