70908-61-1

Phosphonamidates which bear a simple resemblance to penicillin type structures have been synthesised as potential inhibitors of β-lactamases: -ethyl N-(benzyloxycarbonyl) amidomethyl phosphonyl amides, PhCH2OCONHCH2P(O)(OEt)NR2, the amines HNR2 being L-proline, D-proline, L-thiazolidine, and o-anthranilic acid. The proline derivatives completely and irreversibly inactivated the class C β-lactamase from Enterobacter cloacae P99, in a time-dependent manner, indicative of covalent inhibition. The inactivation was found to be exclusive to the class C enzyme and no significant inhibition was observed with any other class of β-lactamase. The anthranilic acid derivative exhibited no appreciable inactivation of the β-lactamases. The phosphonyl proline and phosphonyl thioproline derivatives were separated into their diastereoisomers and their individual second order rate constants for inhibition were found to be 7.72 ± 0.37 and 8.3 × 10-2 ± 0.004 M-1 s-1 for the L-proline derivatives, at pH 7.0. The products of the inhibition reaction of each individual diastereoisomer, analyzed by electrospray mass spectroscopy, indicate that the more reactive diastereoisomers phosphonylate the enzyme by P-N bond fission with the elimination of proline. Conversely, gas chromatographic detection of ethanol release by the less reactive proline diastereoisomer suggests phosphonylation occurs by P-O bond fission. The enzyme enhances the rate of phosphonylation with P-N fission by at least 106 compared with that effected by hydroxide-ion. The pH dependence of the rate of inhibition of the β-lactamase by the more reactive diasteroisomer is consistent with the reaction of the diprotonated form of the enzyme, EH2, with the inhibitor, I (or its kinetic equivalents EH with IH). This pH dependence and the rate enhancement indicate that the enzyme appears to use the same catalytic apparatus for phosphonylation as that used for hydrolysis of β-lactams. The stereochemical consequences of nucleophilic displacement at the phosphonyl centre are discussed.

A series of phosphonochloridates was prepared from the corresponding phosphonate monoesters, and their reactions with alcohols, amines, and the bisnucleophile 4-aminobutan-1-ol have been investigated using 31P NMR spectroscopy. In the conversion of phosphonate monoesters to phosphonochloridates via the addition of thionyl chloride or oxalyl chloride, pyrophosphonate anhydrides were found to be formed readily as byproducts. The anhydrides reacted readily with alcohols, but more slowly than the corresponding phosphonochloridates, and only sluggishly, if at all, with amines. Therefore, when phosphonamides are prepared, anhydride formation must be suppressed. This is accomplished when the monoester is added to the chloridating agent. Unhindered phosphonochloridates reacted predominantly with the amino function of 4-aminobutan-1-ol to furnish the phosphonamidates, whereas a sterically hindered phosphonochloridate demonstrated a preference for O-coupling. This result indictes that the energy gained during P-O bond formation surmounts the kinetic barrier resulting from steric hindrance more effectively than formation of the weaker P-N bond. Importantly, treatment of the phosphonochloridates with tertiary amines prior to addition of the nucleophile resulted in the formation of hitherto unrecognized phosphonylating agents, which we formulated as phosphonyltrialkylammonium salts. The latter, unlike the anhydrides, are more reactive than the phosphonochloridates toward both alcohols and amines, affording improved yields of phosphonate esters and amides. These improved yields are not obtained when triethylamine is added simultaneously with the nucleophile merely to neutralize acid rather than as a deliberate step to generate the phosphonyltrialkylammonium salts. Use of these novel phosphonylating agents proceeded without concomitant racemization at stereogenic centers α to phosphorous. Interestingly, reaction of even an unhindered phosphonyltriethylammonium salt with 4-aminobutan-1-ol favored O-phosphonylation over N-phosphonylation by a factor of 8, demonstrating that both the charge transfer in the transition state and steric hindrance affect the propensity for P-O vis a vis P-N bond formation. In marked contrast, simultaneous addition of this bisnucleophile and triethylamine, like coupling in the absence of tertiary amine, afforded the phosphonate and phosphonamide in nearly equal amounts.

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Acylamino carboxylic acids were degradated by the Hunsdiecker-reaction; the bromo-derivatives were reacted with NaPO(OC2H5)2.Aminophosphonic acids were obtained by acidic hydrolysis, and half-blocked derivatives by the selective removal of masking substituents.Two phosphonopeptides were also prepared by this route.

Diethyl α-aminomethanephosphonate 5a and its α-aryl derivatives 5b-d react with 2,5-diethoxytetrahydrofuran 1 to give diethyl α-pyrrolomethanephosphonate 9a and the α-aryl derivatives 9b-d, respectively.The pyrrolo derivatives 9 can be converted into the lithium salts 15 and 16, respectively, which with carbonyl compounds undergo the Horner reaction yielding E/Z mixtures of N-vinylpyrroles 18.In certain cases the intermediate of the Horner reaction, the β-hydroxyphosphonate, 17 can be isolated.The pyrrolo-analogue of stilbene, 18a, is formed only as E-isomer.On treating the lithium salts 15 and 16 with 9 or with alkyl halides α-C-alkylated pyrrolophosphonates 22 and 23, respectively, are obtained.