Przeglądaj {{ collection }} wg Autor "Hejmanowska, Joanna"

Teraz wyświetlane 1 - 2 z 2

A Convenient Approach to a Novel Group of Quaternary Amino Acids Containing a Geminal Bisphosphonate Moiety
(2014) Dzięgielewski, Marek; Hejmanowska, Joanna; Albrecht, Łukasz
Quaternary amino acids containing a geminal bisphosphonate moiety have been synthesized for the first time. The developed two-step reaction sequence utilizes the Michael addition of α-substituted azlactones to a vinylidene bisphosphonate as the key step. The reaction proceeds under catalytic conditions with excellent regioselectivity. Subsequent, acid-mediated azlactone ring opening affords the target quaternary amino acids with good overall yields. Attempts to develop an enantioselective version of the synthetic strategy are described.
Organocatalytic Enantioselective Approach to Spirocyclic Δβ,γ-Butenolides
(2014) Hejmanowska, Joanna; Dzięgielewski, Marek; Kowalczyk, Dorota; Albrecht, Łukasz
A novel method for the preparation of the spirocyclic Δβ,γ-butenolides is presented. The developed strategy is based on a trienamine-mediated [4+2]-cycloaddition between (E)-3-alkylidene- 5-arylfuran-2(3H)-ones and 2,4-dienals. Target products containing three contiguous centres including one quaternary are efficiently formed in a highly enantiomerically enriched form in the presence of the silyl-protected diphenylprolinol aminocatalyst.