关键词： AZA-CLAISEN REARRANGEMENT   BASE-PROMOTED HYDROLYSIS   ENANTIOSELECTIVECATALYSTS   AMBIENT-TEMPERATURES   1   3 TRANSPOSITION   PLANAR CHIRALITY   AMIDES   DERIVATIVES   FERROCENE   CYCLOPALLADATION  

摘要： Palladium(II) catalysts based on a ferrocenyloxazoline palladacyclic (FOP) scaffold were synthesized and evaluated for the rearrangement of prochiral allylic N-(4-methoxyphenyl)benzimidates. When iodide-bridged dimer FOP precatalysts are activated by reaction with excess silver trifluoroacetate, the allylic rearrangement of both E and Z prochiral primary allylic N-(4-methoxyphenyl)benzimidates takes place at room temperature to give the corresponding chiral allylic N-(4-methoxyphenyl)benzamides in high yield and good ee (typically 81-95%). Several allylic imidate motifs were evaluated also. Because the corresponding enantioenriched allylic amide products can be deprotected in good yield to give enantioenriched allylic amines, allylic N-aryltrifluoroacetimidates were identified as promising substrates.

关键词： SAMARIUM(II) IODIDE   ORGANIC-SYNTHESIS   KETONE   EPOXIDATION   ISOSORBIDE   OLEFINS  

摘要： DIAGRAM A new entry for the asymmetric synthesis of optically active alpha,gamma-substituted gamma-butyrolactones was developed by using a carbohydrate-derived amide as both a chiral auxiliary and a proton source. Unlike the previously reported examples, the chiral auxiliary, employed in this reaction also successfully functioned as a protonating agent. Excellent asymmetric induction could be achieved by this dual stereoselective control in the reaction process.

关键词： 4-COMPONENT CONDENSATIONS   STEREOSELECTIVE SYNTHESIS   CHEMISTRY   ISOCYANIDES   LIBRARIES   ANHYDRIDES  

摘要： DIAGRAM This paper describes the synthesis of a bicyclic beta-amino acid scaffold in both pure enantiomeric forms and its application as chiral auxiliary in an intramolecular version of the Ugi multicomponent reaction (U-5C-4CR) to prepare a-amino acid derivatives of both D- and L-series in a straightforward and very stereoselective manner. The mild conditions required for the Ugi condensation and for the removal of the chiral auxiliary make this method very attractive to prepare a wide range of differently structured N-alkylated and unalkylated amino acid derivatives.

关键词： Alcohols   Peptides and proteins   Reaction products   Monomers   Post-translational modification  

摘要： Practical asymmetric synthesis of functionalized aza-cyclic alpha-amino acid derivatives possessing quaternary stereocenters has been achieved by the phase-transfer-catalyzed alkylation of 2 or 3 using chiral quaternary ammonium bromide 1 as catalyst. Subsequent reduction and alkylation of the 3-keto carbonyl moiety of 4 proceeded with complete diastereochemical control to afford the corresponding beta-hydroxy aza-cyclic alpha-amino acid derivatives having stereochemically defined consecutive quaternary carbon centers.

关键词： ENANTIOMERS   OPTICAL isomers   CHIRAL drugs   CHIRALITY   ASYMMETRY (Chemistry)   CHEMISTRY  

摘要： Both the enantiomers of trans -3-hydroxypipecolic acid have been synthesized employing the Sharpless asymmetric di-hydroxylation and epoxidation as the key steps starting from a commercially available starting material 1,4-butanediol.

关键词： PROSTAGLANDIN synthesis   ASYMMETRIC synthesis   RECEPTOR antibodies   HAY fever   ASYMMETRY (Chemistry)   PROSTAGLANDINS   IMMUNOGLOBULINS   THERAPEUTICS  

摘要： An asymmetric synthesis was developed for the production of a prostaglandin D-2 receptor antagonist for the treatment of allergic rhinitis. The stereogenic center was set using asymmetric allylic alkylation chemistry, and the core of the structure was constructed via Pd-catalyzed N-cyclization/Heck methodology. The synthesis relies on a late stage indoline oxidation which does not racemize the product.

关键词： ENANTIOMERS   OPTICAL isomers   CHIRAL drugs   CHIRALITY   INDOLE alkaloids   ALKALOIDS   ASYMMETRY (Chemistry)   CHEMISTRY  

摘要： We report a novel, facile and asymmetric approach to both enantiomers of the indole alkaloid deplancheine from a readily available, nonracemic chiral template. The natural product and its antipode are isolated with > 95% ee.

关键词： aldol reaction   asymmetric synthesis   Diels-Alder reaction   dienes   polypropionates   sulfur dioxide  

摘要： In the presence of sulfur dioxide and an acid promoter, (-)-(1E,3Z)-2-methyl-1-((1S)-1-phenyleth- oxy)penta-1,3-dien-3-yl isobutyrate reacts with (Z)-3-(trimethylsilyloxy)-pent-2-ene giving a silyl sulfinate intermediate that undergoes, in the presence of palladium catalyst, a desilylation and retro-ene elimination of SO2 with formation of (-)-(1Z,2S,3R,4S)-1-ethylidene-2,4-dimethyl-5-oxo-3-((1S)-1-phenylethoxy)-heptyl isobutyrate as major product. This ethyl ketone undergoes cross-aldol reaction with (2S)2-methyl-3-[(tert-butyldimethylsilyl)- oxy]propanal giving an aldol that is reduced into a stereoheptad corresponding to the C(19)-C(27)-segment of Rifamycins with high diastereoselectivity and enantiomeric excess.

关键词： Alcohols   Anions   Enantioselective synthesis   Pharmaceuticals   Post-translational modification  

摘要： An anionic chiral auxiliary mediated asymmetric alkylation of carbamate 2 provides 3-substituted isoindolinones 4 in high ee. This methodology was used in the first asymmetric synthesis of (+)-lennoxamine.

关键词： Pauson-Khand reaction   alkenyl sulfones   alkenyl sulfoxides   asymmetric synthesis   chiral auxiliary   cyclopentanoid synthesis  

摘要： Unlike other types of electron-deficient alkenes, alkenyl sulfones and alkenyl sulfoxides are excellent alkene partners in Pauson-Khand reactions (PKR). In the case of the intramolecular PKR of appropriately substituted 1-sulfinyl-1,6-enynes and 1-sulfonyl-3-oxygenated-1,6-enynes novel stereoselective processes and applications in asymmetric synthesis have been developed. Furthermore, using the cobalt-chelating dim ethylaminophenyl vinyl sulfoxide as substrate, their intermolecular PKR with terminal alkynes provide the first intermolecular asymmetric version of PKR with non-strained alkenes. The resulting 5-sulfinyl-2-cyclopentenones are versatile intermediates in the enantioselective synthesis of natural cyclopentanoids. 1 Introduction 2 Background: PKR of Electron-Deficient Alkenes 3 Intramolecular PKR of gamma-Oxygenated alpha,beta-Unsaturated Sulfones and Related Enynes 4 PKR of alpha,beta-Unsaturated Sulfoxides 4.1 Intramolecular Processes 4.2 Intermolecular Processes 4.3 Applications to the Enantioselective Synthesis of Natural Cyclopentanoids 5 Summary.