2583-48-4Relevant academic research and scientific papers
Enantioselective organocatalytic addition of oxazolones to 1,1-bis(phenylsulfonyl)ethylene: A convenient asymmetric synthesis of quaternary α-amino acids
Alba, Andrea-Nekane R.,Companyo, Xavier,Valero, Guillem,Moyano, Albert,Rios, Ramon
experimental part, p. 5354 - 5361 (2010/09/15)
A new, easy, and highly enantioselective method for the synthesis of quaternary α-alkyl-α-amino acids based on organocatalysis is reported. The addition of oxazolones to 1, 1-bis(phenylsulfonyl)ethylene is efficiently catalyzed by simple chiral bases or thioureas. The reaction affords α-disubstituted α-amino acid derivatives with complete C4 regioselectivity and with excellent yields and enantioselectivities. This methodology is complementary to previously reported enantioselec-tive approaches to quaternary ot-amino acids and allows the synthesis of αphenyl-α- alkyl-α-amino acids and αiert-butyl-α-alky1-α-amino acids. It has distinct advantages in terms of operational simplicity, enviromentally friendly conditions, and suitability for largescale reactions.
Enantioselective Synthesis of α-Branched α-Amino Acids with Bulky Substituents
Studer, Armido,Seebach, Dieter
, p. 217 - 222 (2007/10/02)
Enantiopure 5,5-disubstituted t-butyl 2-t-butyl-3-methyl-4-oxoimidazolidine-1-carboxylates readily available by diastereoselective double alkylation of the parent compound (Boc-BMI) can be converted to α-branched α-amino acids with two bulky substituents (PhCH2/Et, PhCH2/i-Pr, PhCH2/CH2C6H11) in four simple steps: hydrolysis to the amino acid amides, N-benzoylation, cleavage of the amino acid amide group, and debenzoylation (Scheme 3, products 6-10, overall yields >50percent).This procedure constitutes an extension of the scope of amino acid synthesis from (R)- and (S)-Boc-BMI. - Key Words: Amino acids, α-branched/ Highly hindered amides/ Hydrolysis of amino acid amides/ Anchimeric effect/ Phenylalanine, 2-ethyl, 2-i-propyl- and 2-cyclohexylmethyl-
