改进的1,3-缩水-2,4-二-氧-苄基-β-L-鼠李糖及1,3——缩水-2,4,6-三-氧-苄基-β-D-甘露糖的合成

用相应二丁基锡络合物对α-L-鼠李糖烯丙基苷及α-D-甘露糖烯丙基苷进行选择性3-氧-烯丙基化. 用(Ph~3P)~3RhCl催化脱烯丙基并苄基化得到相应的苄基化1,3-二醇. 再进行乙酰化,氯化,接着进行关环反应,得到1,3-缩水苄基内醚糖.     

SELECTIVE PHOTOOXIDATION OF trans,trans-1, 4-DIPHENYL-1, 3-DIBUTADIENE IN ZEOLITE ZSM-5

本文研究了反式,反式-1,4-二苯基-1,3-丁二烯(DPB)在沸石NaZSM-5中的光敏氧化反应。在溶液中9,10-二氰基蒽(DCA)敏化光氧化反应有两种机制:单重态氧机制和电子转移产生超氧负离子机制。我们把DPB吸附在沸石ZSM-5孔道中,DCA溶解于沸石外部溶剂季戊四醇三甲醚中,溶剂和敏化剂都不能进入沸石孔道。光照反应后,在沸石孔道中只得到DPB的单重态氧的反应产物,没有电子转移的产物产生。反应产物产率为100%。大大提高了反应的选择性。     

醛类与1,2-二(对甲苯胺基)乙烷作用的研究Ⅰ.

1.用1,2-二(对甲苯胺基)乙烷与醛类缩合而得1,3-二(对甲苯基)-2-烃基四氢咪唑,在反应的专属性,缩合手续,产率及产物的熔点范围方面似均较前人用1,2-双苄胺基乙烷,1,2-二(对甲氧苄胺基)乙烷或1,2-二(对氯苄胺基)乙烷为佳. 2.改进1,2-二(对甲苯胺基)乙烷的合成方法,使产量提高,并消除副反应. 3.曾制备二十四种新的1,3-二(对甲苯基)-2-烃基四氢咪唑类化合物,和三种1,2-二(对甲苯胺基)乙烷的衍生物. 4.1,3-二(对甲苯基)-2-邻硝基苯四氢咪唑可用稀盐酸分解为相应的邻硝基苯甲醛和1,2-二(对甲苯胺基)乙烷的二盐酸盐,其反应几为定量.     

寡糖和多糖的合成

本文重点介绍了寡塘及多馆在化学合成方面的进展,述及了寡掂经典合成方法及近年来发展的一些新方法,如三氯乙酸亚胺基作为离去基团的方法,以缩水内醚糖为糖的给体的方法等。对多糖的合成主要介绍了1,6-、1,4-、1,3-、1,2-缩水内醚搪的阳离子聚合制备均聚多塘,及用糖原酸醋衍生物通过缩聚反应制备多塘。     

改进的1,3-缩水-2,4-二-氧-苄基-β-L-鼠李糖及1,3-缩水-2,4,6-三-氧-苄基-β-D-甘露糖的合成

己糖的1,3—缩水内醚衍生物由于与在生理上有重要作用的血凝聚素TXA_2(ThromboxaneA_2)含有相同的2,6—dioxabicyclo[3.1.1]heptane的骨架,而受到化学界、生物化学界的重视。此外,它们的立体有规聚合,然后脱保护基,能得到(1→3)连接的多糖,后者是多糖的生物化学实验的宝贵的基准物。近年来,本研究组致力于1,3—缩水内醚糖衍生物的合成及构象研究,及由其制备寡糖、多糖的研究,先后合成了D—鼠李糖,L—鼠李糖,D—半乳     

一个异常的反应-顺式的二氟芪与二氟卡宾反应生成反式的环加成物

在光敏剂(丁二酮,0.05mol.dm^-^3)存在下,75%的反式1,2-二氟芪通过光化学异构化转化成顺式1,2-二氟芪,由Seyferth试剂(PhHgCF3)产生的二氟卡宾(CF2)与顺式和反式芪的反应是立体专一性环加成反应,遵循Skell规则.然而,尽管CF2与反式1,2-二氟芪反应得到反式1,2-二苯基全氟环丙烷(9),顺式1,2-二氟芪与二氟卡宾反应仍然得到相同的反式环加成物,这一异常现象,可能是由于高度活化的三元环中CF2对面的C-C键均裂而产生的.     

一个异常的反应——顺式的二氟茋与二氟卡宾反应生成反式的环加成物

在光敏剂(丁二酮,0.05mol·dm~(-3))存在下,76％的反式1,2-二氟芪通过光化学异构化转化成顺式1,2-二氟芪.由Seyferth试剂(PhHgCF_2)产生的二氟卡宾(CF_2)与顺式和反式芪的反应是立体专一性环加成反应,遵循Skell规则.然而,尽管CF_2与反式1,2-二氟芪反应得到反式1,2-二苯基全氟环丙烷(9),顺式1,2-二氟芪与二氟卡宾反应仍然得到相同的反式环加成物,这一异常现象,可能是由于高度活化的三元环中CF_2对面的C—C键均裂而产生的.     

内醚糖——Ⅶ.关于2,3-内醚-D-阿罗糖吡喃甙转化为3,6-内醚-D-葡萄糖吡喃甙的实驗証据

应用四步合成反应证实,在Haworth的吡喃糖甙透视结构中与C_6-侧链处于反位的2,3-内醚环可以在碱性试剂作用下转化为相应的3,6-内醚糖甙,为Ohle所提出的推论提供确切的实验证据。四步反应包括由2,3-二-O-对甲苯磺酰基-D-葡萄糖一α-甲基呲喃甙(ⅩⅢ),经三苯甲基化,得糖浆状的2,3-二-O-对甲苯磺酰基-6-O-三苯甲基-D-葡萄糖-α-甲基吡喃甙(ⅪⅤ)。然后应用Purdie-Irvine的方法进行甲基化,得结晶的2,3- 二-O-对甲苯磺酰基-4-O-甲基-6-O-三苯甲基-D-葡萄糖-α-甲基吡喃甙(ⅩⅤ);在乙酸酐中以乙酰溴置换ⅩⅤ的三苯甲基,生成糖浆状的2,3-二-O-对甲苯磺酰基-4-O-甲基-6-O-乙酰基-D-葡萄糖-α-甲基吡喃甙(ⅩⅥ)。再直接在氯仿中在0°用甲醇钠处理,得到两种结晶产物;其一为水溶性的2,3-内醚-4-甲基-D-阿罗糖-α-甲基吡喃甙(ⅪⅩ),另一为溶于有机溶剂中的2,3-二-O-对甲苯磺酰基-4-O-甲基-D-葡萄糖-α-甲基吡喃甙(ⅩⅦ)。两者的结构均经彻底甲基化为已知的结晶的2,3-内醚-4,6-二-O-甲基-D-阿罗糖-α-甲基吡喃甙(ⅩⅪ)和2,3-二-O-对甲苯磺酰基-4,6-二-O-甲基-D-葡萄糖-α-甲基吡喃甙(ⅩⅧ),加以确定。将2,3-内醚-4-O-甲基-D-阿罗糖-α-甲基吡喃甙(ⅪⅩ)在1N氢氧化钠溶液中处理得到54％产率的3,6-内醚-4-O-甲基-D-葡萄糖-α-甲基吡喃甙(ⅩⅩ),与Haworth,Owen和Smith由3,6-内醚-D-葡萄糖-α一甲基吡喃甙经部分甲基化而得的产物相同。对吡喃糖甙中的2,3-内醚环转化为3,6-内醚环体系进行了简单的构象分析。     

(Z)-1,2-二苯基-1,3-丁二烯与单取代的乙烯衍生物区位选择性环加成反应

(Z)-1,2-二苯基-1,3-丁二烯分别与甲基乙烯基酮、丙烯酰胺、丙烯腈以及丙烯醛发生环加成反应,均生成顺式和反式的连位取代环己烯衍生物。以IR、¹HNMR和MS鉴定了产物的结构。利用CNDO/2法计算了分子轨道能量和系数,由前线分子轨道理论解释了这种环加成反应的区位选择性。     

1,2-二苯基六氟环丁烷的结构及其热解反应

本文报导了α,β,β-三氟苯乙烯环化二聚物的结构及其热裂解反应的研究.α,β,β-三氟苯乙烯环化二聚物全同于四氟乙烯和1,2-二氟茋的环化加成物,且其质谱中有二氟茋(分子量216)的碎片;因此证明其结构为1,2-二苯基六氟环丁烷(顺式及反式异构体的混合物),即三氟苯乙烯以头对头方式加成的产物.反式1,2-二氟芪或反式芪与四氟乙烯进行热环化加成反应,得到相应的1,2-二苯基六氟环丁烷(反式:顺式约98:2)或1,2-二苯基3,3,4,4-四氟环丁烷(反式).上述反应具有(顺,反)立体选择性.用裂解色谱法研究了1,2-二苯基六氟环丁烷的热裂解反应.在较低温度时(400°以下),主要反应是顺式物异构化为反式物的反应.在400～600°范围内,对称裂解占优势,定量地生成α,β,β-三氟苯乙烯.在高温下(700°以上)则同时有不对称裂解发生.     

Synthesis and Glycosidic Reaction of 1,2-Anhydromanno-, Lyxo-, Gluco-, and Xylofuranose Perbenzyl Ethers

ABSTRACT

Stereospecific synthesis of 1,2-anhydromanno-, lyxo-, gluco-, and xylofuranose perbenzyl ethers was successfully achieved via intramolecular S _N2 reaction of the corresponding C-1 alkoxide with C-2 bearing tosyloxy group. The key intermediates, furanose 2-sulfonates, were prepared from the corresponding 1,2-diols and tosyl chloride under phase transfer conditions in good yields. Condensation of the anhydro sugars with 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose or N-benzyloxycarbonyl L-serine methyl ester in the absence of catalyst gave 1,2-trans-linked glycofuranosides in high yield.     

Synthesis of 1,2,4-triazole and thiazole analogs of ketoconazole

The synthesis of 1,2,4-triazole and thiazole analogs of ketoconazole is described in which one of the α azole ring carbons is linked to C-2 of the ketal by means of a three methylene tether. Lithiation of 1-methyl-1,2,4-triazole and thiazole and subsequent alkylation with 2-(2,4-dichlorophenyl)-2-(3-iodopropyl)-1,3-dioxolane produced, after an aqueous acidic workup, 2,4-dichlorophenyl 3-[5-(1-methyl-1,2,4-triazolyl) and 2-thiazolyl]propyl ketones, respectively. Ketalization with glycerol furnished the corresponding diastereomeric pairs of cis and trans 1,3- dioxolanes. The reaction of 2,4-dichlorophenyl 3-[5-(1-methyl-1,2,4-triazolyl)]propyl ketone with 3-mercapto-1,2-propanediol produced the corresponding diastereomeric cis and trans hydroxymethyl 1,3-oxathiolanes. The diastereomeric racemates were separated by column chromatography and their stereochemistry established by nOe nmr experiments. Some of these racemic cis ketal alcohols were converted by benzyl bromide to the corresponding benzyl ethers. Several of these racemic cis-ketals were reacted, first with methanesulfonyl chloride, then with 1-acetyl-4-(4-hydroxyphenyl)piperazine, to furnish the title compounds.     

Preparation of alpha-C-glycosides from glycals

[reaction: see text]. A novel approach to simple C-glycosides is reported. Reductive ring opening of 1,2-anhydro sugars with titanocene(III) chloride produces an anomeric radical that can be trapped with a variety of agents. The reaction stereospecifically affords alpha-glycosides and produces a free C-2 hydroxyl group allowing for further elaboration.     

Direct synthesis of 1,6-anhydro sugars from unprotected glycopyranoses by using 2-chloro-1,3-dimethylimidazolinium chloride

Various 1,6-anhydro sugars have been synthesized directly from the corresponding unprotected glycopyranoses in excellent yields by using 2-chloro-1,3-dimethylimidazolinium chloride (DMC) as a dehydrative condensing agent. The reactions took place smoothly under mild reaction conditions in aqueous media. The present method would be a practical tool for synthesis of 1,6-anhydro derivatives of monosaccharides, linear-oligosaccharides, and branched-oligosaccharides.     

1,2-migration of 2'-oxoalkyl group and concomitant synthesis of 2-C-branched O-, S-glycosides and glycosyl azides via 1,2-cyclopropanated sugars

Treatment of 2'-oxoalkyl 2-O-Ms(Ts)-alpha-C-mannosides (4, 5, and 6) with base resulted in 1,2-cyclopropanation via an intramolecular SN2 reaction due to their 1,2-trans-diaxial configurations. The 1,2-cyclopropanated sugars (10 and 13) were reacted with various alcohols, thiols, and sodium azide to produce 2-C-branched O- and S-glycosides and glycosyl azides (11, 14-28) in good to excellent yields. In contrast, 1,2-cis 2'-oxoalkyl 2-O-Ms(Ts)-alpha-C-glucoside 9 formed an acyclic conjugated aldehyde (31) under basic conditions, which occurred by 1'-enolation followed by beta-elimination. An intramolecular Michael addition from 31 produced 2-O-Ms-beta-C-glucoside 30 as a major product. However, due to the electron-withdrawing effect exerted by 2-O-Ms compound 31 also undergoes a C2 epimerization to form 32. Thereafter, the intramolecular Michael addition led to the formation of both 1,2-trans 2'-oxoalkyl 2-O-Ms-alpha-C-mannoside 4 and its beta-anomer (33). Because beta-elimination/Michael addition and C2 epimerization are reversible reactions, equilibriums among 9, 31, 30, 32, 33, and 4 were established, which included the transformation of 1,2-cis C-glucoside 9 into 1,2-trans C-mannoside 4. The subsequent 1,2-cyclopropanation of 4 was an irreversible reaction yielding 1,2-cyclopropanated 10 and further conversion to 1,2-migration products (11 and 12).     

Synthesis of oxepane ring containing monocyclic, conformationally restricted bicyclic and spirocyclic nucleosides from D-glucose: a cycloaddition approach

Carbohydrate-derived substrates having (i) C-5 nitrone and C-3-O-allyl, (ii) C-4 vinyl and a C-3-O-tethered nitrone, and (iii) C-5 nitrone and C-4-allyloxymethyl generated tetracyclic isoxazolidinooxepane/-pyran ring systems upon intramolecular nitrone cycloaddition reactions. Deprotection of the 1,2-acetonides of these derivatives followed by introduction of uracil base via Vorbrüggen reaction condition and cleavage of the isooxazolidine rings as well as of benzyl groups by transfer hydrogenolysis yielded an oxepane ring containing bicyclic and spirocyclic nucleosides. The corresponding oxepane based nucleoside analogues were prepared by cleavage of isoxazolidine and furanose rings, coupling of the generated amino functionalities with 5-amino-4,6-dichloropyrimidine, cyclization to purine rings, and finally aminolysis.     

Asymmetric total synthesis of botcinins C, D, and F

Stereoselective total synthesis of botcinins C, D, and F is effectively carried out through asymmetric aldol reactions, 6-endo ring closure, and SmI2-mediated 3,4-trans or -cis stereoselective intramolecular Reformatsky reaction. Rapid esterification of the main skeleton of botcinins with the chiral side chain using MNBA and DMAP produced botcinin D, an antifungal chemical against a pathogen of rice blast disease.     

Synthesis of 3-(5-Aryl-1,3,4-oxadiazol-2-yl)chromones

A general procedure was proposed for the synthesis of 3-(5-aryl-1,3,4-oxadiazol-2-yl)chromones by reaction of 3-formylchromone with aroylhydrazines, transformation of the corresponding acylhydrazones into 1,3-dipoles by the action of bromine in the presence of sodium acetate, and intramolecular ring closure.