Synthesis of Chiral Azacrown Ethers Derived from a-D-Glucose and Their Catalytic Properties on the Asymmetric Michael Addition
2001; Elsevier BV; Volume: 55; Issue: 1 Linguagem: Inglês
10.3987/com-00-9098
ISSN1881-0942
AutoresToshiyuki Itoh, Shohei Shirakami,
Tópico(s)Molecular spectroscopy and chirality
ResumoThree types of chiral azacrown ethers have been synthesized from (+)-(4,6-O-benzylidene)-O-methyl-α-D-glucopyranoside and their catalytic properties for the asymmetric Michael addition have been investigated; enantioselectivity switching which is dependent on the azacrown ether catalysts has been achieved.Development of a natural environmentally friendly catalyst for the asymmetric reaction is one of the current topics in recent organic synthesis; 1 several types of efficient catalysts derived from alkaloids 2 or chiral crown ethers 3 have been reported with their numerous applications. 2,3We are attracted by chiral azacrown ethers which were derived from sugars reported by Töke and his colleagues. 4We have previously demonstrated a simple method for resolving axially chiral biphenyldicarboxylic acids based on the kinetic controlled cyclic ester formation of racemic biphenyldicarboxylic acids with (+)-( 4,6-Obenzylidene)-O-methyl-α-D-glucopyranoside. 5 In the reaction, two adjacent hydroxyl groups at the 2and 3-positions on the glucoside had an important role in recognizing chirality.5b,6 MeO MeO O O Me O O O N O H MeO O O OMe OMe O O O N H Figure1. Results of MO(PM3) calculation of the optimized structure of two azacrown ethers 1a and 2a derived from α-D-Glucose 1a (2,3-type) 2a (3,4-type)Although no mechanistic detail for the origin of enantio-favoritism of Töke's sugar-type azacrown ether has been reported, we expected that opposite enantioselectivity could be seen between the 2,3-bridged
Referência(s)