不同溶剂中氟原子对糖苷键立体选择性的影响

在乙腈等5种不同溶剂中,以2,3,4-O-三苄基-6-O-(2-氟苄基)-β-对甲基苯基-D-葡萄糖硫苷作为糖基供体,甲醇作为受体,并以糖基化供体2,3,4,6-O-四苄基-β-对甲基苯基-D-葡萄糖硫苷为对照,研究了在葡萄糖硫苷C-6位引入氟取代基对糖苷键立体选择性的影响。结果表明,引入的2-氟苄基与普通苄基保护基相比,β构型比例都有一定程度的提高,其中当溶剂为乙腈时,β构型比例较在其他溶剂中提升最明显,α/β比值可达到1/4.7。     

铑(II)催化重氮苄基膦酸酯与芳香亚胺的氮杂环丙烷化反应

铑(II)催化重氮苄基膦酸酯与芳香亚胺反应, 一步合成氮杂环丙烷-2-膦酸酯. 该方法立体定向地得到唯一的反式构型产物, 反应历程是重氮化合物先与亚胺形成叶立德中间体, 然后发生自身环丙烷化反应.     

高立体、区域选择性合成(Z)-1-芳硫基-2-芳硒基烯

氢氧化铯催化下,四氢呋喃作溶剂,室温、氮气保护下,炔基硫醚与硒酚发生亲核加成反应,立体选择性合成一系列(Z)-1-芳硫基-2-芳硒基烯,收率70%～93%.反应机理为氢氧化铯与硒酚反应产生的芳硒化铯,随后对炔硫醚进行亲核加成,形成的烯基负离子水解得到产物.     

核苷研究2: 苄基糖核苷的立体选择性合成

1-(2, 3, 4, 6-O-四苄基吡喃糖基)-三氟乙酸酯或三氯乙酸酯在无水四氯化锡存在下与一些具有代表性的硅醚保护的碱基或者含氮杂环化合物反应, 合成了一系列新的苄基糖苷。对三氟乙酰氧基、三氯乙酰氧基作为新的离去基在核苷合成中的反应活性、立体选择性和反应收率进行了讨论。     

核苷研究2: 苄基糖核苷的立体选择性合成

1-(2, 3, 4, 6-O-四苄基吡喃糖基)-三氟乙酸酯或三氯乙酸酯在无水四氯化锡存在下与一些具有代表性的硅醚保护的碱基或者含氮杂环化合物反应, 合成了一系列新的苄基糖苷。对三氟乙酰氧基、三氯乙酰氧基作为新的离去基在核苷合成中的反应活性、立体选择性和反应收率进行了讨论。     

环戊-2-烯酮的研究Ⅰ.环戊-2-烯酮与醛反应的区域选择及非对映立体选择性

本文系统研究了环戊-2-烯酮在碱性条件下与醛类的羟醛缩合反应,并通过结构及过渡状态的分析,解释了所得的这类反应的区域及非对映立体选择性.     

1.6-缩水-2,4-二-氧-苄基-β-D-吡喃葡萄糖合成、开环及立体选择性成苷反应研究

以较好产率合成了3-位具有不同保护基的1,6-缩水-2,4-二-氧-苄基-β-D-吡喃葡萄糖,并对其开环反应以及成苷反应的立体选择性进行了研究.     

硝基烷基膦酸酯碳负离子烷基化反应区域选择性研究

α-或β-硝基烷基膦酸酯双负离子与卤代烷反应, 生成碳-烷基化产物, 反应区域选择性取决于硝基膦酸酯的结构, 讨论了可能的反应机理。     

Asymmetric synthesis of alpha-methylphosphophenylalanine derivatives using sulfinimine-derived enantiopure aziridine-2-phosphonates

[formula: see text] 2-Methylaziridine-2-phosphonates were prepared from enantiopure sulfinimines and were demonstrated to be versatile synthetic intermediates for the synthesis of novel alpha-disubstituted and alpha,beta-trisubstituted alpha-aminophosphonate derivatives. The first asymmetric synthesis of both enantiomers of alpha-methylphosphophenylalanine is described.     

An efficient synthesis of diethyl coumarin-3-phosphonates

A general synthesis of a number of diethyl coumarin-3-phosphonates (3) has been achieved using titanium tetrachloride-pyridine as the condensing agent.     

Direct and stereoselective synthesis of alpha-linked 2-deoxyglycosides

alpha-Linked 2-deoxyglycosides were conveniently obtained by employing a glycosyl donor having a participating ( S)-(phenylthiomethyl)benzyl moiety at C-6, whereas 2,6-dideoxy-alpha-glycosides could be prepared by BF 3.Et 2O-promoted activation of allyl glycosyl donors.     

Regioselective synthesis of 4-alkylquinolines from quinoline via 1-ethoxycarbonyl-1, 2-dihydroquinoline-2-phosphonates

1-Ehtoxycarbonyl-1, 2-dihydroquinoline-2-phosphonates ($\text{3}$) were treated with n-butyllithium followed by alkyl halides to afford the corresponding 4-alkylated phosphonates ($\text{7}$) with complete regioselectivity in 67–97% yields. The phosphonates ($\text{7}$) were converted to 4-alkylquinolines ($\text{8}$) in ca. 50% yields by treatment with sodium iodide in HMPA or by alkaline hydrolysis in aqueous ethanol.     

3-取代芳基-2-吲哚基膦酸酯的合成

本文根据Fischer吲哚合成法制备了一系列的3-取代芳基-2-吲哚基膦酸酯. 盐酸苯肼与o,o-二异丙基-4-氯-苯乙酰基膦酸酯在无水酒精中反应, O,O-二异丙基-(4'-氯苯-3H-吲哚-2-膦酸酯能被分离出来, 而且它的异构化最终产物能被观察到.     

Ring transformations of aziridinyl 2-phosphonates: synthesis of 5-phosphono-2-oxazolidinones and 5-phosphono-2-imidazolidinones

Syntheses of 5-phosphono-2-oxazolidinones and 5-phosphono-2-imidazolidinones were achieved from the corresponding 1-vinyl-2-phosphonoaziridines. Regioselective aziridine ring opening employing methyl chloroformate affords 1-amido-2-chloroethylphosphonates, which were easily transformed into the corresponding 2-oxazolidinones upon heating in dimethyl sulfoxide. Treatment of the aziridine ring opening products with ammonia furnishes vinylphosphonates, which undergo a Michael type addition with several amines. In situ ring closure of the addition products yields the corresponding phosphonylated 2-imidazolidinones.     

Regio- and stereoselective synthesis of functionalized N-Boc-2-alkynylcyclopropylamines

Russian Chemical Bulletin -     

Improved asymmetric synthesis of aziridine 2-phosphonates using (S)-(+)-2,4,6-trimethylphenylsulfinamide

The aza-Darzens reaction of lithium diethyl iodomethylphosphonate with enantiopure N-(2,4,6-trimethylphenylsulfinyl)imines affords a single diastereomeric N-sulfinylaziridine 2-phosphonate which, on treatment with MeMgBr, gives the corresponding NH-aziridine 2-phosphonate chiral building blocks. An improved asymmetric synthesis of (S)-(+)-2,4,6-trimethylphenylsulfinamide is also given.     

Asymmetric synthesis of polyfunctionalized pyrrolidines from sulfinimine-derived pyrrolidine 2-phosphonates. Synthesis of pyrrolidine 225C

[reaction: see text] The Horner-Wadsworth-Emmons reaction of aldehydes with sulfinimine-derived 3-oxo pyrrolidine phosphonates represents a new method for the asymmetric synthesis of ring-functionalized cis-2,5-disubstituted 3-oxo pyrrolidines.     

Recent advances in the stereoselective synthesis of carbohydrate 2-C-analogs

C-branched carbohydrates are of current interest for glycochemistry, are widely found in nature and serve as important subunits in many antibiotics, bacterial polysaccharides and macrolides. Among C-functionalized saccharides, 2-C-branched carbohydrates represent challenging structures for synthetic chemists, since in contrast to C-glycosides they are not easily accessible from glycosyl bromides or other simple precursors. In this perspective we want to summarize recent approaches to 2-C-branched carbohydrates over the past fifteen years. The two main strategies are based on ring-opening of 1,2-cyclopropanated carbohydrates by various reagents, as well as radical additions to glycals and further transformations, developed in our group. Both methods are characterized by high stereoselectivities and good yields and give access to a broad variety of functionalized carbohydrate 2-C-analogs.