55544-88-2Relevant academic research and scientific papers
Completion of the spectroscopical data for the synthesis of DIMBOA
Handler, Norbert,Erker, Thomas
, p. 95 - 100 (2005)
Cyclic hydroxamic acids like 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin- 3(4H)-one (DIMBOA) and 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA) are found in several plants playing an important role in the defense-system of plants against a variety of enemies. To investigate new mechanism and effects we synthesized the molecules using known synthetic pathways. Since the chemical data of DIMBOA are not complete or even false, we decided to publish the missing ones in this journal. O?sterreichische Apotheker-Verlagsgesellschaft m. b. H.
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.
