Dirhodium catalyzed reactions of aryl-substituted tetrahydropyranone diazoacetoacetates produce ylide intermediates that unexpectedly yield two oxabicyclo[4.2.1]-nonane diastereoisomers, but a single diastereoisomer is formed by increasing the steric bulk of the aryl substituent.

Abstract A method for the synthesis of functionalized piperidines containing 3 contiguous stereocentres in 2-,3- and 4- positions uses a diastereoselective nitro-Mannich to control stereochemistry. The reaction between β-aryl/heteroaryl substituted nitroalkanes glyoxylate imine provides β-nitro-amines with good selectivity (70:30 >95:5) syn, anti-diastereoisomers. Reductive cyclisation BF3.OEt2...

A series of structurally diverse spiro 1,3-oxazines were conveniently prepared from three-component reaction conjugated imines, dialkyl acetylenedicarboxylates (DAAD), and N,N'-disubstituted parabanic acids in dry dichloromethane without catalyst. Initially, various imines synthesized aniline derivatives with cinnamaldehyde. Subsequently, DAAD N,N'-substituted led to mixture the corresponding s...

Both 1-methylisopropyl 2-(2-hydroxyethyl)piperidine-1-carboxylate, (Picaridin((R))) and cyclohex-3-enyl 2-methylpiperidin-1-yl ketone (AI3-37220; 220) have two asymmetric centers, and the four diastereoisomers of each compound are known to have differing degrees of mosquito-repellent activity according to quantitative behavioral assays conducted at the United States Department of Agriculture. C...

Oligo-Tröger bases are auspicious scaffolds of molecular engineering, which motivates studies on the mechanism of their interconversion and on the facile determination of the relative configuration of their diastereoisomers. Protonated, sodiated, and argentated species of those compounds were therefore studied via ion-mobility mass spectrometry (IM-MS), allowing differentiation on the basis of ...

Cyclododecane adopts a square-like structure with corner and edge CH(2) groups. In this study erythro- and threo-1,2-difluorocyclododecanes were prepared to explore whether the two vicinal C-F bonds, with different relative configurations, preferably locate at corner/edge or edge/edge locations. Conformational analysis comparing the diastereoisomers was explored by using a combination of (19)F{...

The asymmetric synthesis of gamma-azido trans-cyclopropyl ketones is accomplished via a short, simple and efficient sequence. The cyclopropanation step is achieved by an intramolecular nucleophilic ring closure, with a diphenylphosphinate leaving group, to give trans-cyclopropane exclusively. beta-Keto-diphenylphosphine oxides cyclise to form optically active dihydrofurans. All possible diaster...

The ammonium-directed, metal-free oxidation of 3-(N,N-dibenzylamino)cyclohex-1-ene with mCPBA in the presence of either trichloroacetic acid or tosic acid has been used as the key step to facilitate the synthesis of all the diastereoisomers of 3-aminocyclohexane-1,2-diol, in >98% de in each case.

The reaction of readily available optically active Si-tethered tris(malonates) with C60 gave easily separable diastereoisomers differing by the absolute configuration of the inherently chiral addition pattern on the fullerene core. The absolute configuration of the e,e,e addition pattern has been unambiguously determined using X-ray crystal structure analysis.