Borohydride reduction of the imine groups in a pyruvate-derived cobalt(III) complex, (OC-6-33')-[Co(Aim(2)trien)](2)[ZnCl(4)], occurs with high diastereoselectivity. The major diastereoisomeric product, (OC-6-33'-ARSSR,CSRRS)-[Co(A(2)trien)]Cl has been isolated and crystallographically characterised. The results from base-induced isomerisation of the major isomer allow us to conclude that most ...

The stereochemical course of the oxidation of chiral oxazolidinone-substituted enecarbamates has been studied for singlet oxygen ((1)O(2)), dimethyldioxirane (DMD), and m-chloroperbenzoic acid (mCPBA) by examining of the special structural and stereoelectronic features of the enecarbamates. Valuable mechanistic insight into these selective oxidations is gained. Whereas the R(1) substituent on t...

Substituted seven-membered N-heterocycles are prevalent bioactive epitopes and useful synthons for preparing enzyme inhibitors or molecular recognition systems. To fully exploit the chemical properties of this flexible N-heterocycle scaffold, efficient methods for its diverse functionalization are required. Here we utilize the late-stage oxidation of tetrahydroazepines as an approach to access ...

The (R)-BINOL•SnCl4-catalyzed formal (3 + 2) cycloaddition between 3-substituted indoles and benzyl 2-trifluoroacetamidoacrylate is a direct, enantioselective method to prepare pyrroloindolines from simple starting materials. However, under the originally disclosed conditions, the pyrroloindolines are formed as mixtures of diastereomers, typically in the range of 3:1 to 5:1 favoring the exo-pro...

Fmoc-protected trans-4-methylproline was synthesized starting from D-serine. The chiral scaffold of serine in the form of olefinated Garner's aldehyde 3 was used to control the diastereoselective formation of the new stereocenter on the hydrogenation of allylic alcohol 4. The diastereoselectivity (syn/anti ratio) of the process was 86:14, attained with Raney nickel. Hydrogen migration seems not...

Nucleophilic substitution reactions of five-membered ring acetals bearing fused rings reveal that subtle changes in the structure of the fused ring can exert dramatic influences on selectivity. If the fused ring did not constrain the five-membered ring undergoing substitution, selectivity was comparable to what was observed for an unconstrained system (≥92% diastereoselectivity, favoring the pr...

An oxidative Pd-catalyzed intra-intermolecular dioxygenation of (aza-)alkenols has been reported, with total regioselectivity. To study the stereoselectivity, different chiral ligands as well hypervalent-iodine compounds have compared. In particular, by using a C-6 modified pyridinyl-oxazoline (Pyox) ligand and hypervalent iodine bearing an aromatic ring, excellent enantio- diastereoselectivity...