R- or S-configured 1,2-diol precursors are formed in good yields (54–86 %) and with excellent enantioselectivities (94 to 99 % ee) by using a simple one-pot sequence—catalytic α-aminoxylation of aldehydes followed situ reduction NaBH4—with L- D-proline as the catalyst nitrosobenzene oxygen source (see scheme). Supporting information for this article is available on WWW under http://www.wiley-vch.de/contents/jc_2002/2003/z52097_s.pdf from author. Please note: The publisher not responsible...

The development of syntheses providing enantiomerically pure α-amino acids has intrigued generations chemists and been the subject intense research. This report describes a general approach to functionalized based on catalytic asymmetric synthesis. Proline catalyzed Mannich-type reactions N-PMP-protected α-imino ethyl glyoxylate with variety unmodified ketones provide in high yields excellent regio-, diastereo-, enantioselectivities. Study seven examples yielded six product ee values ≥99%....

Structural and mechanistic studies show that when the selection criteria of immune system are changed, catalytic antibodies have efficiency natural enzymes evolve, but much more accepting a wide range substrates. The were prepared by reactive immunization, process whereby changed from simple binding to chemical reactivity. This yielded aldolase approximated rate acceleration enzyme used in glycolysis. Unlike enzyme, however, antibody aldolases catalyzed variety aldol reactions...

This paper describes the substrate specificity, synthetic scope, and efficiency of aldolase catalytic antibodies 38C2 33F12. These use enamine mechanism common to natural Class I enzymes. Substrates for these catalysts, 23 donors 16 acceptors, have been identified. The aldol acceptor specificity is expected be much broader than that defined here since all aldehydes tested, with exception polyhydroxylated aldehydes, were substrates antibodies. 33F12 shown catalyze intermolecular...

A novel, facile, and highly enantioselective Brønsted acid-catalyzed α-hydroxylation of β-dicarbonyl compounds with up to 99:1 er using nitroso as the oxygen source has been developed. The results disclosed herein considerably extend substrate scope for α-aminoxylation, allowing expeditious, straightforward, efficient access valuable α-hydroxy-β-dicarbonyl highest levels enantiocontrol.

A novel organocatalytic asymmetric tandem Michael−Henry reaction catalyzed by 9-amino-9-deoxyepiquinine (VI) has been developed. The was efficiently catalyst VI to give highly functionalized cyclohexanes with four stereogenic carbons including two quaternary stereocenters in excellent enantioselectivities (97 >99% ee) and high diastereoselectivities (93:7−99:1 dr). Thus, the first Henry of common ketones as acceptors is shown.

Catalyst for THOught: The title reaction using acyclic nitroalkenals the asymmetric installation of both CO and CN bonds led to functionalized tetrahydro-1,2-oxazines (THOs) having up three stereogenic centers; products were isolated in 90 % yield with excellent enantioselectivity complete diastereoselectivity (see scheme). DFT calculations reveal an unprecedented transition state containing a molecule water, which assists bond-forming step by participating two hydrogen bonds.

A highly enantio- and diastereoselective organocatalytic domino Michael−Henry process for the preparation of synthetically unique medicinally important bicyclo[3.2.1]octane derivatives with four stereogenic centers including two quaternary stereocenters has been developed. Theoretical DFT calculations on transition states have carried out to reveal origins excellent stereoselectivities. novel dual model was thus proposed.

Abstract The combination of a transition‐metal catalyst and organocatalyst was designed to achieve highly enantioselective system for the allylic dearomatization reaction naphthols with racemic secondary alcohols. desired β‐naphthalenones, bearing an all‐carbon quaternary center, were obtained in good yields high chemo‐ enantioselectivities. cooperative catalytic system, involving chiral iridium complex phosphoric acid, provided measurable improvements yields, enantioselectivities relative...

A chiral N-heterocyclic carbene (NHC)-catalyzed Diels–Alder reaction of 2-oxoindolin-3-ylidenes and α-chloroaldehydes was developed for the synthesis fused pyrano[2,3-b]indoles in good to excellent yields (up 99%) with high cis-diastereoselectivities (>99:1 dr) enantioselectivities >99% ee).

A chiral N-heterocyclic carbene (NHC)-catalyzed [3 + 3] cycloaddition reaction of imines and oxindole-derived enals was developed for rapid access to spirocylic oxindoles. In most cases, the desired oxindole products were obtained in high yields excellent enantioselectivities with less than 1 h time.

Abstract Described herein is an imidazole ring formation strategy for the synthesis of axially chiral N‐arylbenzimidazoles by means phosphoric acid catalysis. Two sets conditions were developed to transform two classes 2‐naphthylamine derivatives into structurally diverse N‐arylbenzimidazole atropisomers with excellent chemo‐ and regioselectivity as well high levels enantiocontrol. It worth reflecting on unique roles played nitroso group in this domino reaction. functions a linchpin first...

Diaryl ethers are widespread in biologically active compounds, ligands and catalysts. It is known that the diaryl ether skeleton may exhibit atropisomerism when both aryl rings unsymmetrically substituted with bulky groups. Despite recent advances, only very few catalytic asymmetric methods have been developed to construct such axially chiral compounds. We describe herein a dynamic kinetic resolution approach via Brønsted acid catalyzed atroposelective transfer hydrogenation (ATH) reaction...

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTAntibody-Catalyzed Enantioselective Robinson AnnulationGuofu Zhong, Torsten Hoffmann, Richard A. Lerner, Samuel Danishefsky, and Carlos F. BarbasView Author Information The Skaggs Institute for Chemical Biology the Department of Molecular Scripps Research 10550 North Torrey Pines Road, La Jolla, California 92037 Laboratory Bioorganic Chemistry Sloan-Kettering Cancer 1275 York Avenue, New York, 10021 Cite this: J. Am. Chem. Soc. 1997, 119, 34,...

A highly enantioselective and diastereoselective domino organocatalytic double Michael reaction which provides expedited access to multifunctionalized five-membered rings catalyzed by 9-amino-9-deoxyepiquinine (V) has been developed. Simple operational procedures, high yields (81−92%), excellent enantioselectivity (90−97% ee), diastereoselectivities (95:5−>99:1 dr), immense potential of synthetic versatility the products render this new methodology appealing for asymmetric synthesis.

Highly functionalized cyclopentanes with four stereogenic carbons including two quaternary stereocenters have been synthesized in excellent yields (90−95%) complete diastereoselectivities and enantioselectivities (88−96% ee) by the organocatalyzed asymmetric domino Michael−Henry reaction.

A remarkable organocatalyst that facilitates the asymmetric Michael addition of cyclic ketones to nitroolefins in excellent stereoselectivities (98:2 >99:1 dr, 92% >99% ee) has been developed and afforded various types optically active nitroalkane derivatives synthetic biological importance. The extremely simple practical operational procedure at room temperature increases attractiveness this reaction.

Extraordinary levels of stereocontrol were achieved in an efficient organocatalytic asymmetric [3+2]-cycloaddition reaction between α-isothiocyanato imide and various methyleneindolinones. Simple precursors used for the rapid construction spirocyclic oxindole derivatives with high enantiopurity structural diversity, thus providing a new avenue significance to medicinal chemistry diversity-oriented synthesis. Detailed facts importance specialist readers are published as "Supporting...

Under control: The first example of chiral amino phosphine catalysts for the title reaction between vinyl ketones and N-sulfonyl-1-aza-1,3-dienes has been developed. ambient conditions, this protocol provides straightforward access to densely functionalized, enantioenriched tetrahydropyridines with high levels sterecontrol in good excellent yields. Detailed facts importance specialist readers are published as "Supporting Information". Such documents peer-reviewed, but not copy-edited or...

A chiral cooperative catalysis of NHC and Brønsted acid for a formal [4+2] reaction unprotected isatins enals was developed the direct synthesis spiro[indoline-3,2′-pyran]-2,6′(3′<italic>H</italic>)-diones in good to excellent yields (up 95%) with high enantioselectivities &gt;93% ee).

Abstract An organocatalytic atroposelective strategy for accessing enantioenriched axially chiral IAN analogues was developed the first time. A class of novel atropisomeric C2‐arylquinoline skeletons were synthesized with high enantiocontrol via phosphoric‐acid‐catalyzed heteroannulation in situ generated vinylidene ortho ‐quinone methide (VQM) intermediates ‐aminophenones. The tolerated a broad substrate scope, providing facile approach to good yields and excellent enantioselectivities...

Abstract Great efforts have been made in the activation of a C(alkenyl)-H bond vicinal to directing group proceed via five- or six-membered endo -metallocycles. In stark contrast, functionalization geminal exo -metallocycle pathway continued be elusive. Here we report selective transformation an olefinic C-H that is bearing valuable hydroxyl, carbamate amide into C-C bond, which proceeds through four- eight-membered -palladacycles. Compared reported mechanisms proceeding only -palladacycles...