ORGN 525 |
Methods for chemical asymmetric phosphoryl transfer
| Simon Jones, Alan Rolfe, and Ian Wilson. Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, United Kingdom |
Several approaches are described targeting asymmetric phosphoryl transfer employing stoichiometric and catalytic methods. N-Phosphoryl oxazolidinones 1 have been prepared and found to function well as phosphorylating agents. However, asymmetric variants gave poor enantioselectivities, and a mechanistic rationale for this elucidated by preparing substrates bearing a stereogenic phosphorus centre. Two catalytic approaches are also described. The first employs a chiral titanium based Lewis acid in addition to triethylamine as a proton scavenger. Preliminary results have been obtained giving a small but repeatable enantiomeric excess of the residual alcohol. The second approach uses chiral supramolecular nucleophilic catalysts 2 that function by adopting a conformation 3 that places key stereogenic elements along the trajectory of approach of an incoming alcohol nucleophile. Preliminary studies with achiral catalysts have shown rate acceleration in the phosphoryl transfer reaction.  |
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