New Synthetic Route to Phosphonic Acid Anhydrides

Abstract Phosphonic acid anhydrides are useful condensation reagents in the peptide and polyamide synthesis [1,2]. A new method for the preparation of well defined anhydrides is now described and intermediates of the peptide synthesis are elucidated. Cryoscopic and mass spectrometric data confirm the suggested cyclic trimeric molecular structure and the 31P{1H}- as well as 1H-NMR spectra can be explained with the structures: Reaction of t-BuP(O)(SiMe3)2 and PhBCl2 yields the mixed anhydride of t-butylphos-phonic and phenylboronic acid C40H57B4O12P4. The compound forms colourless crystals and the obtained data are in agreement with a 16 membered P-0-B- ring.