β-Lactam derivatives are produced through intermediate donor-acceptor cyclopropene intermediates in high yield, exclusive cis-diastereoselectivity, and high enantiocontrol in a chiral dirhodium carboxylate catalyzed intramolecular C-H functionalization reaction of enoldiazoacetamides.

1) Formation of an oxazolidin-5-one intermediate, subsequent decarboxylation under relatively mild conditions to a stable azomethine ylide, rearrangement to the corresponding Amadori product and final beta β-elimination to afford AA. This pathway can be considered marginal (1-5%) versus the classical Amadori route. In this case, the rate limiting step is the β-elimination reaction. Other groups...

Asymmetric allylation of (hetero)aromatic aldehydes by a zinc(II)-allylbutyrolactone species catalyzed by a chiral BINOL-type phosphoric acid gave β-substituted α-methylenebutyrolactones in 68 to >99% ee and 52-91% isolated yield. DFT studies on the intermediate Zn2+-complex - crucial for chiral induction - suggest a six-membered ring intermediate, which allows the phosphoric acid moiety to act...

The B(C6F5)3-catalyzed silylative reduction of conjugated nitriles has been developed to afford synthetically valuable β-silyl amines. The reaction is chemoselective and proceeds under mild conditions. Mechanistic elucidation indicates that it proceeds by rapid double hydrosilylation of the conjugated nitrile to an enamine intermediate which is subsequently reduced to the β-silyl amine, thus fo...

The TMSOTf-mediated synthesis of β-configured spirocyclic 2-substituted-2-oxazoline ribosides was achieved using a "Ritter-like" reaction in toluene through nucleophilic addition of electron-rich nitriles to the oxacarbenium ion intermediate of 1,2;3,4-di-O-isopropylidene-β-D-psicofuranose derivatives with concomitant intramolecular trapping of the C2 hydroxymethyl group on the electrophilic ni...

The development of new approaches to obtain optically pure β-hydroxy esters is an important area in synthetic organic chemistry since they are precursors of other high value compounds. Herein, the kinetic resolution of racemic β-hydroxy esters using a planar-chiral DMAP derivative catalyst is presented. Following this procedure, a range of aromatic β-hydroxy esters was obtained in excellent sel...

background: many efforts have been undertaken until now to find an alternative approach to packed red cell tranfusion in major β-thalassemia. augmentation of fetal hemoglobin by hydroxyurea has proved to be less effective in this condition as compared to sickle cell anemia, probably due to molecular heterogeneity of the former disease. hydroxyurea efficacy and its relation to xmn1 polymorphism ...

Measuring 802.15.4 reception in three testbeds, we find that most intermediate links are bursty: they shift between poor and good delivery. We present a metric to measure this link burstiness and name it β. We find that link burstiness affects protocol performance and that β can predict the effects. We show that measuring β allows us to reason about how long a protocol should pause after encoun...