Heterocyclic compounds are the omnipresent structural cores comprising many natural and pharmaceutical products of biological significance. Significantly, heterocyclic compounds are widely distributed in nature, and also have applications in agrochemicals, sanitizers, as dyestuff, as copolymers, etc. Among heterocyles, flavonoids are a class of compounds that are highly interesting and constitute many natural products. In general, all flavanoids contains a basic core of C₆‐C₃‐C₆ of phenyl‐benzopyran backbone. The relative placement of the phenyl group on to the benzopyran core makes further classification into flavanoids, isoflavanoids and neoflavanoids. Flavans (2‐aryl chroman) are subclass of anthoxanthanes exhibits a broad spectrum of biological properties such as anti‐inflammatory, anti‐oxidant, and anti‐malarial properties. Some representative naturally occurring products possessing flavan core are apigenin, luteolin, tangeretin, scutellarein, etc. On the other hand, some of the notable isoflavan‐based natural products are glabridin and (S)‐(−)‐equol. Glabridin is isolated from Licorice roots, which regulates paraoxonase (PON₂) levels. While the simple isoflavan (S)‐(−)‐equol, is produced from soy isoflavone intake. Also, natural products such as dalbergichromene, centchroman, and (+)‐myristinin A possess neoflavan (4‐aryl‐3,4‐dihydro‐2H‐chromenes) core structure. Owing to their broad biological and pharmacological properties, synthetic chemists are fascinated in developing new routes toward their synthesis. As a result, a decent number of reports have been established in the literature. Thus, for the past 5 years of time frame, many new methodologies have been witnessed, for the synthesis of various flavan systems. This review emphasizes most of the significant methods on accomplishing flavans, isoflavans and neoflavans and also focused on their applications to the synthesis of relevant natural as well as biologically active products.

中文翻译：

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黄烷，异黄烷和新黄烷的合成新进展

杂环化合物是无所不在的结构核心，包括许多具有生物学意义的天然和药物产品。重要的是，杂环化合物在自然界中广泛分布，并且还用于农用化学品，消毒剂，染料，共聚物等中。在杂环化合物中，类黄酮是一类非常令人感兴趣的化合物，并且构成许多天然产物。一般而言，所有黄酮类化合物的基本核心均为C _6- C _3- C ₆苯基苯并吡喃骨架。苯基在苯并吡喃核上的相对位置进一步分类为类黄酮，异类黄酮和新类黄酮。黄烷酮（2-芳基苯并吡喃）是蒽氧蒽的子类，具有广泛的生物学特性，例如抗炎，抗氧化和抗疟疾特性。具有黄烷核心的一些代表性天然产物是芹菜素，木犀草素，橘皮素，黄cut苷等。另一方面，一些基于异黄烷的天然产物是麦草精和（S）-（-）-雌马酚。Glabridin从甘草的根中分离出来，可调节对氧磷酶（PON ₂）的水平。而简单的异黄酮（S）-（-）-雌马酚是从大豆异黄酮的摄入中产生的。此外，天然产物（如达柏四氢萘，三聚氰胺和（+）-肉豆蔻苷A）具有新黄烷（4-芳基-3,4-二氢-2 H-色烯）核心结构。由于其广泛的生物学和药理特性，合成化学家着迷于开发合成的新途径。结果，在文献中已经建立了大量的报告。因此，在过去的五年时间里，已经见证了许多用于合成各种黄烷系统的新方法。这篇综述重点介绍了完成黄烷，异黄烷和新黄烷的大多数重要方法，并着重介绍了它们在相关天然和生物活性产品合成中的应用。