Characterization of the Isochromen-4-yl-gold(I) Intermediate in the Gold(I)-Catalyzed Glycosidation of Glycosyl ortho-Alkynylbenzoates and Enhancement of the Catalytic Efficiency Thereof
Characterization of the Isochromen-4-yl-gold(I) Intermediate in the Gold(I)-Catalyzed Glycosidation of Glycosyl ortho-Alkynylbenzoates and Enhancement of the Catalytic Efficiency Thereof
复制标题
金(I)催化糖基原炔基苯甲酸酯糖苷化反应中异色烯-4-基-金(I)中间体的表征及其催化效率的提高
DOI：
10.1002/anie.201103409
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发表时间：
2011-01-01
影响因子：
16.6
通讯作者：
Yu, Biao
中科院分区：
文献类型：
--
作者：
Zhu, Yugen;Yu, Biao
我们最近开发了一种新的糖基化方案与糖基邻炔基苯甲酸酯作为供体和金（I）配合物（例如，[Ph 3 PAuOTf]，OTf= O3 SCF 3）作为催化剂。[1]这种金（I）催化的糖基化方法的能力和通用性已在各种糖苷键的有效构建以及复杂寡糖和糖缀合物的全合成中得到证实。[1-6]此外，前所未有的活化机制赋予了该方案独特的优点，包括：1）没有竞争性亲核物种（其通常在经典糖基化反应中出现在离去实体或促进剂中），这使得糖基化引发的四氢呋喃聚合能够顺利进行;[3] 2）缺乏劣化亲电物种（例如在经典糖基化反应中用作促进剂的软刘易斯酸性物质），使易受亲电体影响的黄酮醇3-OH衍生物高效糖基化;[4]和3）温和和接近中性的条件，这使得极酸不稳定的糖苷配基，如N-Boc-保护的嘌呤衍生物（Boc=叔丁氧羰基）和达玛烷衍生物。[5，6]该糖基化方案是基于方案1中描述的机理原理开发的。[1b]用金（I）络合物（例如，[Ph 3 PAuOTf]）活化位于供体A中的邻炔基苯甲酸酯部分中的C13 C三键导致异色烯-4-基-金（I）络合物D和糖氧碳正离子B。通过亲核受体HNu捕获推定的糖氧碳正离子物质B或相关中间体[7]，得到糖苷C。从HNu释放的H+然后将乙烯基金（I）络合物D脱乙酰化以产生异香豆素E，并再生活性AuI物种以完成催化循环。金（I）物质对C13 C三键的亲核攻击活化已经被报道用于许多金（I）催化的转化。[8]最近，一些提议的乙烯基
We have recently developed a new glycosylation protocol with glycosyl ortho-alkynylbenzoates as donors and a gold (I) complex (eg,[Ph3PAuOTf], OTf= O3SCF3) as catalyst.[1] The power and versatility of this gold (I)-catalyzed glycosylation method have been demonstrated in the effective construction of a wide variety of glycosidic linkages and the total synthesis of complex oligosaccharides and glycoconjugates.[1–6] Moreover, the unprecedented activation mechanism has endowed this protocol with unique merits, including 1) the absence of competitive nucleophilic species (which usually occur in the leaving entity or promoter in classical glycosylation reactions), which enables glycosylation-initiated polymerization of tetrahydrofuran to proceed smoothly;[3] 2) the lack of deteriorative electrophilic species (such as the soft Lewis acidic species used as promoters in classical glycosylation reactions), which enables flavonol 3-OH derivatives vulnerable toward electrophiles to be glycosylated efficiently;[4] and 3) the mild and nearly neutral conditions, which allow the extremely acid-labile aglycones, such as the N-Boc-protected purine derivatives (Boc= tert-butoxycarbonyl) and dammarane derivatives, to be glycosylated effectively.[5, 6]This glycosylation protocol has been developed on the basis of mechanistic rational as depicted in Scheme1.[1b] Activation of the CÀC triple bond positioned in the oalkynylbenzoate moiety in donor A with a gold (I) complex (eg,[Ph3PAuOTf]) led to isochromen-4-yl-gold (I) complex D and sugar oxocarbenium ion B. Capture of the putative sugar oxocarbenium species B or related intermediates [7] by the nucleophilic acceptor HNu provided glycoside C. The H+ released from HNu then protodeaurated the vinyl gold (I) complex D to give isocoumarin E with regeneration of the active AuI species to complete the catalytic cycle. Activation of a CÀC triple bond with gold (I) species toward nucleophilic attack has been reported for numerous gold (I)-catalyzed transformations.[8] Recently, a few of the proposed vinyl