关键词： asymmetric synthesis   hydrogen transfer   photochemistry   solid-state chemistry   topochemistry  

摘要： Due to the matrix effect of the crystal lattice, irradiation of ketone 1 yields 2 diastereoselectively as the main product (97% de). Furthermore, the chiral crystal environment in single crystals of 1 (space group P2(1)2(1)2(1)) also renders the reaction enantioselective (86% ee). Both enantiomers of alcohol 2 could be produced, depending on which enantiomorphic form of the chiral crystal was irradiated. As the ketone 1 is achiral and the chiral induction is caused exclusively by physical influences, this reaction represents a further example of an absolute asymmetric synthesis.

关键词： Ethers   Rearrangement   Vinyl   Stereochemistry   Cyclopropanation  

摘要： Rhodium N-(dodecylbenzenesulfonyl)prolinate [(Rh-2(S-DOSP)(4) (1)]-catalyzed decomposition of diazobutenoates in the presence of vinyl ethers results in highly diastereoselective and enantioselective synthesis of donor/acceptor-substituted vinylcyclopropanes. Diethylaluminum chloride-induced rearrangement of these vinylcyclopropanes results in the formation of cyclopentenes with excellent control of diastereoselectivity and for the fused cyclopentenes good control of absolute stereochemistry. This study illustrates the synthetic utility of Rh-2(S-DOSP)(4) as a chiral catalyst for vinylcarbenoid cyclopropanations and the remarkable diastereocontrol that is possible in the diethylaluminum chloride-induced ring expansion of donor/acceptor-substituted vinylcyclopropanes.

关键词： aldol reactions   antitumor agents   bryostatin   total synthesis  

摘要： The potent bryostatin antitumor agents are currently in phase II clinical trials for the treatment of a variety of forms of cancer. Aldol reactions and directed reductions are among the essential steps for the formation of fragments A-C in the total synthesis of the title compound. Coupling of these fragments by sulfone-based olefination and alkylation reactions was followed by macrocyclization and introduction of the enoate moieties on rings B and C.◆ (© 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.)

关键词： 不对称合成   L-焦谷氨酸   手性源   焦谷氨酸  

摘要： 简介了Ｌ－焦谷氨酸作为手性源的反应特点，综述了Ｌ－焦谷氨酸作为手性源在不对称合成中的应用。

关键词： asymmetric synthesis   nitrogen heterocycles   N-acyliminium ions   PCP site ligands   pharmacological enantioselectivity  

摘要： A new method for the asymmetric synthesis of 1-substituted tetrahydroisoquinolines is presented. It is based on stereoselective addition reactions of organometallic compounds to the intermediate N-acyliminium ion 6, which is provided with an N-acyl group as a chiral auxiliary. In addition reactions with organomagnesium and organozinc reagents diastereoselectivities from 70:30 to 95:5 (for 7/8) were observed with the zinc reagents in general leading to markedly improved stereoselectivities. By catalytic hydrogenation of 7 and 8 and after removal of the chiral auxiliary the target compounds 11 and 12 were obtained. The enantiomerically pure 11c-g and 12c-g (ee > 99 %), 1-aryl-tetrahydroisoquinolines, were evaluated for their affinity to the PCP [1-(1-phenylcyclohexyl)piperidine] binding site of the NMDA (N-methyl D-aspartate) receptor. In each case the enantiomers 11 exhibited a higher affinity than those of 12, with the potencies of the enantiomers differing by a factor of 4 (11/12g) to 27 (11/12c). The absolute configuration of the more potent enantiomers 11 is in accordance with the stereochemical requirement found for FR 115427 (3) which is a close analogue.

关键词： Ligands   Genetics   Phosphorus   Addition reactions   Molecular structure  

摘要： The organopalladium complex containing ortho-metalated (S)-( 1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary has been used successfully to promote the asymmetric [4 + 2] Diels-Alder reaction between 3,4-dimethyl-1-phenylphosphole and 2-vinylpyridine. The pyridyl group in the resulting phosphanorbornene cycloadducts can be located stereospecifically in the exo or endo position by controlling the electronic properties of the organopalladium promoter. In the exo-cycloaddition process, the P-N bidentate ligand (-)-2-[(1 alpha,2 alpha(S),4 alpha,7S)-5,6-dimethyl-7-phenyl-7-phosphabicyclp[2.2.1]hept-5-ene-2-yl]pyridine was produced stereoselectively. In the endo-cycloaddition process, however, a pair of separable diastereomeric palladium template complexes containing the naphthylamine auxiliary and the enantiomeric forms of 2-[(1 alpha,2 beta(R/S),4 alpha,7(R/S)-5,6-dimethyl-7-phenyl-7-phosphabicyclo-[2.2.1]hept-5-ene-2-yl]pyridine were obtained. In these diastereomeric complexes, the endo-cycloadducts coordinated on palladiun as monodentate ligands via only their phosphorus donor atoms. The pyridyl-nitrogen atoms are not involved in metal complexation. The absolute configurations and the coordination properties of the exo- and endo-pyridylphosphines have been established by single-crystal X-ray analyses.

关键词： Zirconium   Homoenolate-equivalent   Tetrahydrofurans   Asymmetric synthesis  

摘要： 1-Aza-2-zirconacyclopent-4-enes 3, prepared from α,β-unsaturated imines 2 were used as homoenolate-equivalents to generate 3-aza-1-oxa-2-zirconacyclohept-4-enes 4 via the diastereoselective insertion of prochiral, sterically demanding ketones. Hydrolysis of the zirconacycles using our pyridinium-N-oxide method led to the formation of 4,4,5-substituted 4-phenyltetrahydro-2-furanyl-Narylamines 5 in high diastereomeric purity. A simple method for their conversion into α-methoxytetrahydrofurans 6a-g by treatment with methanol/THF and catalytic amounts of TsOH was developed. The α-methoxytetrahydrofurans 6a-g were easily transformed into 2,2,3-substituted 2,3-dihydrofurans 7 in good overall yields using an acidic elimination step. Benzyl protected γ-butyrolactols 6h-j could be generated in a one-pot procedure. Additionally, first efforts to perform this synthesis enantioselectively are described.

关键词： Group 14 compounds   Carbene complexes   Inorganic compounds   Stereochemistry   Molecular structure  

摘要： Chiral silanes and stannanes can be obtained with high optical purity from the 1,1-addition reactions of nonchiral silanes and stannanes With Fischer carbene complexes substituted with a chiral imidazolidinone auxiliary. The alpha-stannyl imidazolidinone products will undergo transmetalation and alkylation with, high stereoselection with reactive electrophiles.

关键词： 聚合物试剂   手性试剂   有机合成   不对称合成   合成  

摘要： 聚合物支载的有机合成反应比相应的小分子合成体系有独特的优越性．我院有机化学研究室多年来在制备聚合物试剂和催化剂及其在有机合成反应中的应用进行了系统研究，并且在聚合物试剂和催化剂在不对称有机合成反应中的应用研究方面亦取得重要成果。