Efficient synthesis of optically active 1-(2-carboxymethyl-6-ethylphenyl)-1H-pyrrole-2-carboxylic acid: a novel atropisomeric 1-arylpyrrole derivative

Synthesis and Application of New, Optically Active Compounds as Catalysts and Ligands in Enantioselective Reactions

“…2) [7,[22][23][24]. The absolute configurations of the pure optical isomers of 3a-d were determined by combined application of CD spectroscopy and quantum chemical calculations or X-ray diffraction measurements [7,[22][23][24].…”

“…17). Applicability of these catalysts depended on the acidity of the carbon atom next to the phosphorus in 21 and the reactivity of the Michael acceptors (23). The chiral backbone of the catalysts involved R,R-TADDOLs (α,α,α',α'-tetraaryl-1,3-dioxolane-4,5-dimethanols) (23a and 23f) derived from the natural L-tartaric acid, D-glucose (23c) and chincona moiety (23e-23g), all obtained from easily available natural sources, while the 1-phenylpyrrole based diol (23b) and 1,1'-bi-2-naphthol (BINOL) catalysts were derived synthetically (23d).…”

Synthesis of new, optically active 1-(substituted aryl)pyrrole derivatives via atropisomerism directed diastereoselective metalation

“…23 In previous studies 20 we have determined the absolute configuration of (R a )-(-)-4. This axial chirality did not change during the introduction of the methyl group into the benzylic position.…”

“…16 Recently a new class of atropisomeric biaryls, namely the family of 1-phenylpyrrole skeleton containing chiral compounds has been developed in our laboratory. [17][18][19][20] The very first member ((S a )-1) (Scheme 1) of this group was prepared from 1-(2-trifluoromethylphenyl)-1H-pyrrole via selective dimetalation carboxylation reaction sequence. Racemic dicarboxylic acid was resolved into the two stable atropisomers 17,21 and the pure enantiomers were used as starting materials of the synthesis of optically active ligands ((S a )-2) (Scheme 1).…”

“…20 Optically active 4 contains a prochiral benzylic group and enantioselective introduction of a substituent into this position could provide us a new chiral building block with both axial and central chirality elements. However, according to our best knowledge, nobody has studied remote lateral metalation of atropisomeric 1-phenylpyrrole derivatives until now.…”