Analogues of the Cyclic Hydroxamic Acid 2,4‐Dihydroxy‐7‐methoxy‐2H‐1,4‐ benzoxazin‐3‐one: Decomposition to Benzoxazolinones and Reaction with . beta.‐Mercaptoethanol.
Analogues of the Cyclic Hydroxamic Acid 2,4‐Dihydroxy‐7‐methoxy‐2H‐1,4‐ benzoxazin‐3‐one: Decomposition to Benzoxazolinones and Reaction with . beta.‐Mercaptoethanol.
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DOI：
10.1002/chin.199130228
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发表时间：
1991-07
期刊：
影响因子：
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通讯作者：
J. Atkinson;P. Morand;J. T. Arnason;H. Niemeyer;H. Bravo
中科院分区：
文献类型：
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作者：
J. Atkinson;P. Morand;J. T. Arnason;H. Niemeyer;H. Bravo
天然禾本科植物环异羟肟酸（2，4-二羟基-1，4-苯并恶嗪-3-酮）的糖苷配基类似物是通过环上取代的α-（邻硝基苯氧基）-α-甲氧基乙酸甲酯的还原环化反应，然后用溴化三硼或溴化三硼脱甲基以显示2-羟基而合成的。通过改变芳环上C-7位的取代基[R= MeO（1），t-Bu（6），Me（7），H（8），Cl（9），F（10），CO_2Me（11 a）]，得到了构效关系系列。测定C-7系列各成员的异羟肟酸和苯酚部分的pKt值。它们在线性自由能关系（LFER）中很好地相关，对于pXal（异羟肟酸）产生p= 0.71（具有< rp）的值，并且对于pK&（苯酚）产生p= 1.6（具有om）的值。ALFER也存在于这些异羟肟酸单分子分解为苯并恶唑啉酮的速率常数和+之间（p=-1.1）。还研究了β-巯基乙醇还原异羟肟酸为内酰胺的速率。发现只有具有富电子芳香环的化合物，特别是氧杂官能团位于异羟肟酸氮原子的帕拉的化合物（化合物1和3-5）具有可测量的还原速率。然而，在该反应期间在D20缓冲液（pD 9）中记录的1H NMR谱显示化合物1、2、6-9（唯一研究的那些）在C-2处形成半硫缩醛，即使仅1具有可测量的被相同硫醇还原的速率。氧杂官能度提供的显着速率增强表明，减少是通过硫醇盐直接攻击共振稳定离子对的异羟肟氮而发生的。目前已知有400多种昆虫对杀虫剂具有抗性。由于抗药性和环境污染问题，作物保护领域的大多数研究人员都认为迫切需要开发新的害虫管理策略，以减少我们对农药的依赖。其中一个重要的研究领域是培育抗虫害的植物品种。2· 3一种植物可以抵抗攻击的原因有很多，包括形态特征，
Analogues of the aglucones of naturallyoccurring cyclic hydroxamic acids (2, 4-dihydroxy-1, 4-benzoxazin-3-ones) from Gramineae (Poaceae) have been synthesizedby the reductive cyclization of the ring-substituted methyl«-(o-nitrophenoxy)-a-methoxyacetates, followed by demethylation of the C-2 methoxy group with BBr3 or BC13 to reveal the 2-hydroxy group. Astructure-activity series was produced by varying the substituent at C-7 on the aromatic ring [R= MeO (1), t-Bu (6), Me (7), H (8), Cl (9), F (10), C02Me (11a)]. The pKt 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 p= 0.71 (with< rp) for pXal (the hydroxamic acid) and p= 1.6 (with om) for pK& (the phenol). ALFER also existed between the rate constants for the unimolecular decomposition of these hydroxamic acids to benzoxazolinones and+(p=-1.1). The rates of hydroxamic acid reduction to lactams by j3-mercaptoethanol were also investigated. It was found that only compounds with electron-rich aromaticrings and specifically an oxa functionality para to the hydroxamic acid nitrogen atom (compounds 1 and 3-5) had measurable rates of reduction.* H NMR spectra recorded during this reaction in D20 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 attackof thiolate on the hydroxamic nitrogen of a resonance-stabilized ion pair.Over 400 species of insects are now known to be resistant to insecticides. 1, 2 Because of the problems of resistance and environmental contamination, most researchers in the area of crop protection agree on the urgency of developing new pest management strategies that reduce our depen-dence on pesticides. One such important area of research is the development of plant varieties resistant to pest at-tack. 2· 3 A plant may be resistant to attack for a number of reasons, including morphological characteristics such