89682-03-1Relevant articles and documents
Serendipitous discovery of α-hydroxyalkyl esters as β-lactamase substrates
Pelto, Ryan B.,Pratt
experimental part, p. 10496 - 10506 (2011/10/18)
O-(1-Carboxy-1-alkyloxycarbonyl) hydroxamates were found to spontaneously decarboxylate in aqueous neutral buffer to form O-(2-hydroxyalkylcarbonyl) hydroxamates. While the former molecules do not react rapidly with serine β-lactamases, the latter are quite good substrates of representative class A and C, but not D, enzymes, and particularly of a class C enzyme. The enzymes catalyze hydrolysis of these compounds to a mixture of the α-hydroxy acid and hydroxamate. Analogous compounds containing aryloxy leaving groups rather that hydroxamates are also substrates. Structure-activity experiments showed that the α-hydroxyl group was required for any substantial substrate activity. Although both d- and l-α-hydroxy acid derivatives were substrates, the former were preferred. The response of the class C activity to pH and to alternative nucleophiles (methanol and d-phenylalanine) suggested that the same active site functional groups participated in catalysis as for classical substrates. Molecular modeling was employed to explore how the α-hydroxy group might interact with the class C β-lactamase active site. Incorporation of the α-hydroxyalkyl moiety into novel inhibitors will be of considerable interest.
Probing host-selective phytotoxicity: Synthesis and biological activity of phomalide, isophomalide, and dihydrophomalide
Ward, Dale E.,Vazquez, Alfredo,Soledade,Pedras
, p. 1657 - 1666 (2007/10/03)
The cyclic depsipeptide phomalide [cyclo(Val-(E)-Aba-Hpp-Hmp-(R)-Leu); Aba = 2-amino-2-butenoic acid, Hpp = (2S)-2-hydroxy-3-phenylpropanoic acid, Hmp = (2S)-2-hydroxy-4-methylpentanoic acid] is the host-selective phytotoxin produced by the fungus [Leptosphaeria maculans (Desm.) Ces. et de Not., asexual stage Phoma lingam (Tode ex Fr.) Desm.] which causes blackleg disease (a devastating disease of several economically important brassica crops). Efficient total syntheses of phomalide, its (Z)-isomer isophomalide, and the two dihydro analogues [(R)-dihydrophomalide and (S)-dihydrophomalide] are described. A [2 + 3] fragment coupling of Cbz-Val-(Z)-Aba with Hpp-Hmp-D-Leu-OBn followed by deprotection and cyclization gave isophomalide which was diastereoselectively isomerized to phomalide by conjugate addition of PhSeH followed by elimination of the corresponding selenoxide. The dihydro analogues were prepared similarly using Cbz-Val-(R)-Abu or Cbz-Val-(S)-Abu (Abu = 2-aminobutanoic acid) in place of Cbz-Val-(Z)-Aba. Biological evaluations of phomalide, isophomalide, and the dihydrophomalides revealed that only phomalide (10-5 M) caused necrotic, chlorotic, and reddish lesions on canola (Brassica napus and Brassica rapa; susceptible to blackleg) leaves whereas no damage was observed on brown mustard (Brassica juncea; resistant to blackleg) or white mustard (Sinapis alba; resistant to blackleg) leaves, even at significantly higher concentrations (10-4 M). Thus, both the presence and configuration of the double bond is crucial for selective phytotoxicity. This is the first reported synthesis of an (E)-Aba-containing natural product, and importantly, the (Z) → (E) isomerization approach should be applicable to other (depsi)peptide targets thereby allowing investigation of the effect of the double-bond configuration on various properties.
Transition state analogy of phosphonic acid peptide inhibitors of pepsin
Bartlett, Paul A.,Giangiordano, Mark A.
, p. 3433 - 3438 (2007/10/03)
A series of 11 phosphonate peptide analogs, RO2C-Xaa-Yaa-Phe-{PO2--O}-Phe O-(3-(4-pyridyl)propyl ester), were synthesized and evaluated as inhibitors of the aspartic peptidase pepsin. For the inhibitors with Gly or Ala at the P2 position, the K(i) values correlate with the K(m)/k(cat) values of the corresponding substrates, demonstrating that these analogs mimic the transition state in the way the P2-P4 residues bind. Deviations from the correlation for the other inhibitor/substrate pairs imply a different binding orientation as a result of N-substitution at P2 (Pro), contamination with the more potent diastereomer (D-Ala), or a change in rate-limiting step for turnover (Ile).
