Naringenin (1, Scheme 1) is a flavanone belonging to a part of a huge group of bioactive polyphenols. In order to selectively modify desired phenol/s, in this study, we developed some methods for selective protections of three hydroxy groups of 1. The 1st method is to silylate two hydroxy groups of 1 and then selectively de-protect the silylation product followed by site-selective acetylation, or site-selective silylation of 7-OH and then acetylation of 4’-OH. The 2nd synthetic method was started from triacetyloxylated naringenin (10), which was conducted in specific solvents to remove the distinctive acetyl protection by TFA, TsOH or imidazole. After protection of 4’,5-dihydroxynaringenin (12) by TBS at 7-OH to form 7-t-butyldimethylsilyloxy-4’,5-diacetyloxynaringenin (13), in the 3rd method, 4’-OAc or 5-OAc of 13 was selectively de-protected under acidic conditions to afford 4’-OH-5-OAc-7-OTBS naringenin (14) or 4’-OAc-5-OH-7-OTBS naringenin (6) as mixed protection derivatives. These methods have the advantages of mild reaction conditions, easily handled reagents and satisfactory yields.

中文翻译：

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柚皮素酚羟基的选择性保护和脱保护

柚皮素（Naringenin）（1 ，方案1）是一种黄烷酮，属于一大类生物活性多酚的一部分。为了选择性地修饰所需的酚，在本研究中，我们开发了一些选择性保护1的三个羟基的方法。第一种方法是对1的两个羟基进行甲硅烷基化，然后选择性地对甲硅烷基化产物进行脱保护，然后进行位点选择性乙酰化，或者对7-OH进行位点选择性甲硅烷基化，然后对4'-OH进行乙酰化。第二种合成方法是从三乙酰氧基化柚皮素( 10 )开始，进行 在特定溶剂中去除TFA、TsOH 或咪唑独特的乙酰基保护。4',5-二羟基柚皮素( 12 )在7-OH处被TBS保护形成7-叔丁基二甲基甲硅烷氧基-4',5-二乙酰氧基柚皮素( 13 )后，在第三种方法中，4'-OAc或5-OAc 13在酸性条件下选择性脱保护，得到4'-OH-5-OAc-7-OTBS柚皮素( 14 )或4'-OAc-5-OH-7-OTBS柚皮素( 6 )作为混合保护衍生物。这些方法具有反应条件温和、试剂易于操作、收率满意的优点。