We report the development, analysis and use of a new combinatorial approach to analyze the substrate sequence dependence of the suicide inhibition, cyclization, and reverse cyclization reactions catalyzed by a group I intron from the opportunistic pathogen Pneumocystis carinii. We demonstrate that the sequence specificity of these Internal Guide Sequence (IGS)-mediated reactions is not high. In...

Key words cyclization - specialty peptides natural products continuous flow acylammonium

Key words (‒)-exiguolide - macrolide marine natural product macrocyclization ring-closing metathesis transannular cyclization

We have developed a Ni-catalyzed cascade cyclization/Negishi-coupling reaction for the formation of pyrrolidines and pyrrolidinones starting from N-protected allylamines acrylamides which contain redox active ester group. The provides two C-C bonds in single operation takes place with both alkylzinc arylzinc bromides as nucleophiles. Activation RAE by low valent Ni complexes involving radical p...

A novel Cu(II)-catalyzed cyclization of α-diazo-β-oxoamides with amines has been developed, constituting a straightforward method to construct pyrrol-3(2H)-one rings. The intramolecular hydrogen bonding effect in α-diazo-β-oxoamides plays an essential role in this reaction. A plausible reaction mechanism involving divergent generation and subsequent [2 + 3] cyclization of ketene and α-diazoimin...

Intramolecular cyclization of nitrogen-tethered alkynyl esters catalyzed by phosphazene organosuperbases P2-tBu and P4-tBu was investigated. Both acyclic and cyclic substrates underwent 5-exo-dig and 5-endo-dig cyclization. This reaction is a rare example of the intramolecular addition of enolates of simple esters to alkynes.

A concise, diastereoselective total synthesis of (±)-cortistatin J has been completed in 20 steps from furan. Key steps include an intramolecular [4 + 3] cyclization of a disubstituted furan with a (Z)-2-(trialkylsilyloxy)-2-enal to construct the tetracyclic core and a (Z)-vinylsilane/iminium ion cyclization to form the A ring.

Optically active stannolanes and trigonal bipyramidal pentacoordinated tin complexes were readily prepared by radical cyclization of N-propargylated chiral aza-Morita-Baylis-Hillman adducts induced by Bu(3)SnH. A translocated radical through the cyclization attacked the Bu(3)Sn group in an S(H)2 manner.

An efficient silver-catalyzed oxidative cyclization of acrylamides with 1,3-dicarbonyl compounds is described. It proceeds through a tandem radical addition/cyclization process, in which two new C-C bonds were formed. Furthermore, the same concept can also be extended to the reaction of easily available ketones and acrylamides.

Cyclization of 1,6-diynes promoted by stoichiometric Ga(III) halides produces vinyl halides in good to excellent yields. Under acidic conditions, initially formed iodocyclization products undergo in situ Friedel-Crafts cyclizations, giving access to iodoindenopyridines. Application of the vinyl halides in cross-coupling reactions has been explored, and mechanistic aspects of the cyclization are...