Diastereoselective Synthesis of Heteroaromatic Glycine Derivatives

Abstract

A TMSOTf promoted addition of an N-tert-butanesulfinyl α-imino ester to five-membered aromatic heterocycles furnishes optically active heteroaromatic glycine derivatives with moderate-to-good yield in diastereomeric ratios up to

Friedel‐Crafts dealkylation reaction mediated by a stereoselective proton transfer in the fragmentation of protonated cyclic indolyl α‐amino esters

“…[1][2][3][4][5][6] As a unique but unnatural scaffold for peptides and peptidomimetics, optically active cyclic α-amino acids with indole functionalization have attracted considerable attention. [7][8][9][10][11][12][13] Recently, Jia and co-workers [14] have successfully synthesized a series of indole-functionalized chiral cyclic α-amino esters by a catalytic asymmetric Friedel-Crafts alkylation reaction, providing an efficient approach to chiral α-tetrasubstituted indolic α-amino acids. Understanding the fragmentation reactions of protonated cyclic indolyl α-amino esters is useful for interpretation and prediction of their intrinsic properties and the fragmentation mechanisms of protonated peptides containing them.…”

“…Indole is one of the most important natural chemical templates occurring in various biologically active molecules and it has been proved to be antiviral, antioxidant, antiproliferative, etc . As a unique but unnatural scaffold for peptides and peptidomimetics, optically active cyclic α‐amino acids with indole functionalization have attracted considerable attention . Recently, Jia and co‐workers have successfully synthesized a series of indole‐functionalized chiral cyclic α‐amino esters by a catalytic asymmetric Friedel‐Crafts alkylation reaction, providing an efficient approach to chiral α‐tetrasubstituted indolic α‐amino acids.…”

Enantioselective Construction of Cyclic Indolyl α‐Amino Esters via a Friedel–Crafts Alkylation Reaction

“…The catalytic asymmetric Friedel–Crafts alkylation reaction provides an efficient access to chiral indole derivatives 13. Although the alkylation of indoles with ketimines using chiral phosphoric acids as catalysts has been reported to afford chiral tertiary amines,14 to the best of our knowledge, the chiral metal complex‐catalyzed Friedel–Crafts reaction between indoles and ketimines has not yet been reported 15. Herein, we report a Friedel–Crafts alkylation reaction of indoles with cyclic N ‐sulfonyl ketimino esters16 that yields cyclic indolyl α‐amino esters in excellent enantioselectivities with the use of a copper‐bisoxazoline complex as a chiral catalyst; this work represents the first example of chiral Lewis acids being applied to asymmetric Friedel–Crafts reactions of ketimines (Scheme ) 17,18…”

Enantioselective synthesis of α-amino esters through Petasis borono-Mannich multicomponent reaction of potassium trifluoroborate salts

“…α-Amino acids are widely found in bioactive natural products and medicinal compounds. 1,2 Since α-amino esters were recognized as main precursors of α-amino acid derivatives, much efforts have been devoted to the synthesis of α-amino esters including organometallics addition [3][4][5] or metal-catalyzed addition reactions, [6][7][8][9] Friedel-Crafts reactions, [10][11][12][13] Mannich reactions, 14,15 Michael additions, 16 hydrogenations, 17,18 [4+2] cycloadditions, [19][20][21][22] and so on. Among them, Petasis borono-Mannich (PBM) reaction highlighted the prominence toward the facile synthesis of α-amino esters in which highly functionalized products were obtained from simple aldehydes, amines, and boronic acid precursors.…”