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近年来,国外有关维生素B_6(以下简称VB_6)新合成路线报道很多,其中以通过双烯加成(Diels-Alder)反应的方法应用最为广泛。即以噁唑类化合物(双烯物)与一亲双烯物进行双烯加成,加成产物经芳构化变为吡啶衍生物,再经数步反应即可制得VB_6,所用原料种类很多,由此构成很多条合成路线。可归纳为以下三种类型: 上列路线的特点是反应步骤短,收率高。自从1962年美国E.E.Harris等发表了由4-甲基-5-乙氧基噁唑与富马腈(或马来酸二乙酯;2,5-二氢呋喃)经三步反应得到VB_6(总收率41.5％),其后不少国家如日本、德国、荷兰、苏联、法国等也纷纷试用不同活
In recent years, there are many new synthesis routes of Vitamin B_6 (hereinafter referred to as VB_6) in foreign countries, of which Diels-Alder reaction is the most widely used method. That is, the oxazole compound (diolefin) and a dienophile are added to the diolefin. The addition product is converted into a pyridine derivative by aromatization, and then VB_6 can be obtained through a few steps of reaction. The raw materials used Many, which constitute a lot of synthetic route. Can be grouped into the following three types: The above routes are characterized by short reaction steps and high yields. Since 1962, EEHarris et al published a three-step reaction of 4-methyl-5-ethoxyoxazole with fumaronitrile (or diethyl maleate; 2,5-dihydrofuran) The total yield of 41.5%), followed by many countries such as Japan, Germany, the Netherlands, the Soviet Union, France, have also tried different live