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The synthesis of fungicidal aminophosphonic acid derivatives

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Volckman, Janis F. (1988) The synthesis of fungicidal aminophosphonic acid derivatives. Doctoral thesis, Polytechnic of North London.

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Abstract

A number of 1-aminoalkanephosphonic acid derivatives incorporating physiologically Iabile groupings (ester, amide e.g. peptide, carbamate and tosyl) were prepared as a development from earlier studies in which certain phosphonic acid derivatives were shown to have previously unrecognised activity as fungicides. Such derivatisation might aid the translocation of the active phosphonic acid to the site of action.

Compounds were screened for in vivo fungicidal activity against Drechslera teres. Drechslera graminae. Drechslera avenae. Prythium ultlmum. Rhizoctonia solani. Fusarium culmorum. Pyricularia oryzae, Puccinia recondita. Erysiphe zraminis[?] and Septoria nodorum. Results showed that all the phosphonopeptides prepared had moderate to good antifungal activity, with the L-alanine di- and tripeptides of l-aminopropanephosphonic acid having superior activity to the commercial fungicide imazalil when tested against D. teres and D. avenae.

The proton, carbon-13 and phosphorus-31 nmr spectroscopy of the compounds prepared was examined in detail with carbon-13 proving particularly useful. The carbon-phosphorus coupling constants varied along the alkyl chain in the phosphonopeptides with JPC=145-148 Hz, JPCC=0 Hz , JPCCC=12-14 Hz and JPCNC=4-6 Hz.

The use of Fast Atom Bombardment mass spectrometry has proven to be successful for the characterisation of aminophosphonic acid derivatives, especially phosphonopeptides, with the MH ion normally being the base peek. Phosphonopeptides give characteristic fragmentation patterns due to the sequential loss of [alpha]-lactam units arising from the amino acid chain.

A number of routes to the preparation of l-aminoalkanephosphonic acids were investigated, in particular those routes utilizing 1-ozo-alkanephosphonates, and a detailed study into the hydrogenation of dialkyl l-hydroxyiminoalkanephosphonates using Raney Nickel and, more successfully, palladiua-on-carbon catalysts was undertaken.

Preliminary attempts were made to prepare phosphonopeptides via the previously unexamined route of solid phase synthesis and some of the difficulties involved with this method are discussed.

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