Stereoselective Synthesis of (<i>E</i>)-Mannosylidene Derivatives Using the Wittig Reaction
作者:Gregory S. Coumbarides、Majid Motevalli、Warda A. Muse、Peter B. Wyatt
DOI:10.1021/jo061178s
日期:2006.9.1
high yields of mannosylidene derivatives; in contrast to the glucose and galactose analogues, the (E)-mannosylidenes are predominant (E:Z > 9:1), thus minimizing dipole−dipole repulsions in the Wittigreactions. NMR indicates chair-like conformations for solutions of the (E)-mannopyranosylidenes, but not for those (Z)-isomers where data are available (EWG = CN or CO2Et). X-ray crystallography shows an
稳定的烷基化物Bu 3 P CH(EWG),其中EWG为酯基或腈基,可与2,3,4,6-四-O-苄基甘露糖醛-1,5-内酯反应,得到高产率的甘露烯衍生物。与葡萄糖和半乳糖类似物相比,(E)-甘露糖基占主导地位(E:Z > 9:1),从而使维蒂希反应中的偶极-偶极排斥力最小。NMR表示(E)-甘露聚糖吡喃酮溶液的椅子样构型,但对于有数据可用的那些(Z)异构体则没有(EWG = CN或CO 2 Et)。X射线晶体学显示四氧的大致扭曲构象-苄基保护的(Z)-亚苄基乙腈。
C-Glycosylidene derivatives (exo-glycals): their synthesis by reaction of protected sugar lactones with tributylphosphonium ylids, conformational analysis and stereoselective reduction
作者:Miguel Gascón-López、Majid Motevalli、George Paloumbis、Peter Bladon、Peter B Wyatt
DOI:10.1016/j.tet.2003.09.081
日期:2003.11
Stabilised tributylphosphonium ylids Bu3PCHCH(EWG), where EWG is CO2Me, CO2tBu or CN, react with protected sugar lactones under mild conditions to give high yields of glycosylidene derivatives (4 and 5) with good Z/E selectivity. X-Ray crystallography shows that in the solid state the tetra-O-benzyl protected (Z)-glucosylideneacetonitrile (Z)-4c adopts a conformation intermediate between a boat and
作者:Long Min、Yang Zhang、Xuefeng Liang、Junrong Huang、Wenli Bao、Chi-Sing Lee
DOI:10.1002/anie.201405770
日期:2014.10.13
2‐pyrone Diels–Alder cycloaddition for the synthesis of the ABD ring system, and finally a highly efficient biomimetic intramolecular O‐acylation for the C ring formation. This result provides an important perspective on the biosynthetic origin of the unprecedented 7‐membered acylketeneacetal moiety of the C ring.
通过研究两种拟议的生物合成途径(O-甲基化和O-酰化),实现了史无前例的7-甲氧基-4,5-二氢-3的高度非对映选择性和实用仿生全合成的(±)-basiliolide B H ‐oxepin‐2‐1(C环)。该合成具有环丙烷化/开环策略,用于在C8和C9建立立体异构中心,仿生2吡喃酮Diels-Alder环加成反应用于ABD环系统的合成,最后是高效仿生分子内O酰化的C环形成。这一结果为C环空前的7元酰基乙烯酮缩醛部分的生物合成起源提供了重要的视角。
Multistep Phase-Switch Synthesis by Using Liquid-Liquid Partitioning of Boronic Acids: Productive Tags with an Expanded Repertoire of Compatible Reactions
作者:Sam Mothana、Jean-Marie Grassot、Dennis G. Hall
DOI:10.1002/anie.200906710
日期:2010.4.6
Tagging along: A system for phase‐switch synthesis has been developed. The boronicacid functionality is used as a phase tag that complexes to sorbitol and facilitates compound transfer from an organic solvent to water at high pH. The phase tag can then be used in a productivereaction step to generate targeted products, thereby eliminating purification by silica gel chromatography.