Asymmetric synthesis of protected arylglycines by rhodium-catalyzed addition of arylboronic acids to N-tert-butanesulfinyl imino esters

A new method for the Rh(I)-catalyzed addition of arylboronic acids to N-tert-butanesulfinyl imino esters has been developed for the asymmetric synthesis of arylglycine derivatives. This method provides high yields (61-90%) and diastereoselectivities (>98:2) for a variety of functionalized arylboronic acids. The N-sulfinyl arylglycine ester products are versatile intermediates for further transformations, including selective protecting group removal, conversion to beta-amino alcohols, and direct incorporation into peptides.     

Graft-copolymerization of styrene on polypropylene in the solid phase

The graft-copolymerization of styrene on PP in the solid phase has been studied under various reaction conditions using a radical initiator. Polymerization kinetics were investigated by DSC experiments and reactions in glass ampoules. The conversion rate and grafting efficiency of styrene appeared to be strongly influenced by the presence of the PP matrix and the styrene/PP ratio. From reactions in a lab scale reactor the concentrations of styrene and initiator, the dosing rate and the temperature were investigated to be critical parameters determining the grafting efficiency and the average length and number of grafts. The phenomena observed were explained by describing the process in relative rates of diffusion and polymerization, including swelling of the polymer by styrene monomer and diffusion limitations (Trommsdorff effect).     

Asymmetric copper-catalyzed synthesis of alpha-amino boronate esters from N-tert-butanesulfinyl aldimines

A general and efficient new method for the asymmetric synthesis of alpha-amino boronate esters has been developed. The key step is the Cu(I)-catalyzed addition of bis(pinacolato)diboron to N-tert-butanesulfinyl aldimines, which proceeds in good yields (52-88%) and with very high diastereoselectivities (>96:2) for a variety of aldimine substrates. This method was applied to an efficient synthesis of bortezomib, a potent alpha-amino boronic acid inhibitor of the proteasome that is in clinical use for the treatment of multiple myeloma and mantle cell lymphoma.     

Catalytic,three-component assembly reaction for the synthesis of pyrrolidines

[reaction: see text] Copper(I) salts catalyze the three-component assembly reaction between an alpha-diazo ester, an imine, and various alkenes and alkynes to form substituted pyrrolidines with excellent to good diastereoselectivities in high yields. The transition metal-catalyzed decomposition of the alpha-diazo compound in the presence of the imine likely generates a transient azomethine ylid that undergoes addition with various dipolarophiles in a highly convergent manner.