85758-42-5Relevant academic research and scientific papers
REACTION OF A CYCLIC HYDROXAMIC ACID FROM GRAMINEAE WITH THIOLS
Niemeyer, Hermann M.,Corcuera, Luis J.,Perez, Francisco J.
, p. 2287 - 2290 (1982)
An insect inhibitor isolated from maize extracts, 2,4- dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), reacted with cysteine, mercaptoethanol, ethanethiol and dithiothreitol.Second order rate constants were 0.54, 0.73 and 1.96 l/mol min for the reaction with cysteine, mercaptoethanol and dithiothreitol, respectively.Products isolated from the reaction of DIMBOA with ethanethiol corresponded to reduction of the hydroxamic acid to amide and/or hemiacetal-hemithioacetal exchange.The reactivity of DIMBOA with sulfhydryl groups of compounds such as cysteine, may be a basis for its inhibitory action on enzymes and its toxicity. - Key Word Index - Zea mays; Gramineae; 1,4-benzoxazin-3-ones; thiols.
Analogues of the Cyclic Hydroxamic Acid 2,4-Dihydroxy-7-methoxy-2H-1,4-benzoxazin-3-one: Decomposition to Benzoxazolinones and Reaction with β-Mercaptoethanol
Atkinson, Jeffrey,Morand, Peter,Arnason, John T.,Niemeyer, Hermann M.,Bravo, Hector R.
, p. 1788 - 1800 (2007/10/02)
Analogues of the aglucones of naturally occurring cyclic hydroxamic acids (2,4-dihydroxy-1,4-benzoxazin-3-ones) from Gramineae (Poaceae) have been synthesized by the reductive cyclization of the ring-substituted methyl α-(o-nitrophenoxy)-α-methoxyacetates, followed by demethylation of the C-2 methoxy group with BBr3 or BCl3 to reveal the 2-hydroxy group.A structure-activity series was produced by varying the substituent at C-7 on the aromatic ring .The pKa values for the hydroxamic acid and the phenol moieties were determined for each member of the C-7 series.They correlated well with ? in a linear free energy relationship (LFER) yielding values of ρ = 0.71 (with ?p) for pKa1 (the hydroxamic acid) and ρ = 1.6 (with ρm) for pKa2 (the phenol).A LFER also existed between the rate constants for the unimolecular decomposition of these hydroxamic acids to benzoxazolinones and ?+ (ρ = -1.1).The rates of hydroxamic acid reduction to lactams by β-mercaptoethanol were also investigated.It was found that only compounds with electron-rich aromatic rings and specifically an oxa functionality para to the hydroxamic acid nitrogen atom (compounds 1 and 3 - 5) had measurable rates of reduction. 1H NMR spectra recorded during this reaction in D2O buffers (pD 9), however, showed that compounds 1, 2, 6 - 9 (the only ones investigated) formed a hemithioacetal at C-2 even though only 1 has a measurable rate of reduction by the same thiol.The remarkable rate enhancement provided by an oxa functionality suggests that reduction occurs by direct attack of thiolate on the hydroxamic nitrogen of a resonance-stabilized ion pair.
