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Your search keyword '"Petri, M. A."' showing total 15 results
Start Over Author "Petri, M. A." Journal angewandte chemie
15 results on '"Petri, M. A."'

1. Dihydrooxazine Oxides as Key Intermediates in Organocatalytic Michael Additions of Aldehydes to Nitroalkenes

Author

Gokarneswar Sahoo, Petri M. Pihko, Mikko Melarto, Hasibur Rahaman, Imre Pápai, Arto Valkonen, and Ádám Madarász

Subjects
chemistry.chemical_classification, chemistry, Organic chemistry, Protonation, General Chemistry, Nuclear magnetic resonance spectroscopy, General Medicine, ta116, Catalysis, Alkyl
Abstract

Pause and play: dihydrooxazine oxides are stable intermediates that are protonated directly, without the intermediacy of the zwitterions, in organocatalytic Michael additions of aldehydes and nitroalkenes (see scheme, R=alkyl). Protonation of these species explains both the role of the acid co-catalyst in these reactions, and the observed stereochemistry when the reaction is conducted with α-alkylnitroalkenes.

Published
2012
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4. Synthesis of the ABCD Ring System of Azaspiracid

Author

K C, Nicolaou, Wenyuan, Qian, Federico, Bernal, Noriaki, Uesaka, Petri M, Pihko, and Jürgen, Hinrichs

Subjects
General Medicine
Abstract

Previously attempted spirocyclizations to form the ABCD ring system of azaspiracid (1) have proven unsuccessful owing to the anomeric effects that favor the formation of the undesired 13S diastereomer. By the use of a hydrogen bond donor as an auxiliary group, such anomeric effects were successfully overcome. Thus, the first synthesis of the ABCD ring system of azaspiracid with the proper 13R configuration of the C13 stereocenter was achieved.

Published
2001
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11. A Catalyst Designed for the Enantioselective Construction of Methyland Alkyl-Substituted Tertiary Stereocenters.

Author

Claraz, Aurélie, Sahoo, Gokarneswar, Berta, Dénes, Madarász, Ádám, Pápai, Imre, and Pihko, Petri M.

Subjects
CHEMICAL inhibitors, NATURAL products, CHEMICAL reactions, ACROLEIN synthesis, ENANTIOSELECTIVE catalysis
Abstract

Tertiary methyl-substituted stereocenters are present in numerous biologically active natural products. Reported herein is a catalytic enantioselective method for accessing these chiral building blocks using the Mukaiyama-Michael reaction between silyl ketene thioacetals and acrolein. To enable remote enantioface control on the nucleophile, a new iminium catalyst, optimized by three-parameter tuning and by identifying substituent effects on enantioselectivity, was designed. The catalytic process allows rapid access to chiral thioesters, amides, aldehydes, and ketones bearing an a-methyl stereocenter with excellent enantioselectivities, and allowed rapid access to the C4-C13 segment of (-)-bistramide A. DFT calculations rationalized the observed sense and level of enantioselectivity. [ABSTRACT FROM AUTHOR]

Published
2016
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