C-2 SYMMETRY ENANTIOPURE PHOSPHOROTHIOATES AND PHOSPHOROTHIOAMIDATES STARTING FROM 2,2',6,6'-BIPHENYLTETROL

A straightforward procedure for the preparation of enantiopure phospho rothioates and diastereopure phosphorothioamidates of 2,2',6,6'-biphen yltetrol is presented. Basic alcoholysis of compounds trans-3 and cis- 3 proceeds in high diastereoselectivity to give only two of the six po ssible acyclic phosphorothioamidates 4a and 4b (or 5a and 5b). When di astereopure 4 and 5 are subjected to acid alcoholysis they lead to ena ntiopure cyclic phosphorothioates trans-6 and trans-7, respectively. A ll compounds prepared are solid, air stable and possess a Ct symmetry axis. Due to restricted rotation around the Cl-Cl' bond, compounds 4a, 4b, 5a, 5b, 6 and 7 exist as stable atropisomers at rt. However for c ompounds trans-3 and cis-3, the bridged biphenyl system intercorverts at rt with a half-life of 6 h. The structure of compounds trans-2, tra ns-3, and 5a has been confirmed by X-ray analysis. Phosphorothioates a nd phosphorothioamidates can be tested as agrochemicals since these cl asses of compounds can inhibit acetylcholinesterase of many different insect species.