78761-19-0

Upstream product

• 5845-61-4 cyclo(L-Ala-L-Ala) 
• 71785-55-2 (3S,6S)-(+)-2,5-Dimethoxy-3,6-dimethyl-3,6-dihydropyrazin 
• 10065-72-2 L-Alanine methyl ester 
• 420-37-1 trimethoxonium tetrafluoroborate 
• 4392-24-9 Cinnamyl bromide 

Downstream Products

• 10065-72-2 L-Alanine methyl ester 
• 78810-45-4 (R)-2-Amino-2-methyl-5-phenyl-4-pentensaeure-methylester 

Relevant academic research and scientific papers

ENANTIOSELECTIVE SYNTHESIS OF NON-PROTEINOGENIC AMINO ACIDS VIA METALLATED BIS-LACTIM ETHERS OF 2,5-DIKETOPIPERAZINES

Bis-lactim ethers 1 of 2,5-diketopiperazines contain a chiral inducing center, an acidic CH-bond and two sites susceptible to hydrolysis.They react with BuLi to give Li compounds of type 4, 15, 29 or 32, which possess a prochiral C atom.They readily add electrophiles (such as alkylating agents or carbonyl compounds) with unusually high diastereoface differentiation.In many cases the d.e-value (d.e. = diastereomeric excess = asymmetric induction) of the adduct exceeds 95percent.On hydrolysis the adducts are cleaved liberating the chiral auxiliary (used to build up the bis-lactim ether 1) and the target molecules, the optically active amino acid methyl esters of type 8, 19, 25 or 36.The two amino acid esters are separable either by fractional distillation or (eventually after further hydrolysis to amino acids) by chromatography.Transition state models are discussed that could explain the exceptionally high asymmetric induction and the predictability of the induced configuration.

Asymmetric Syntheses via Heterocyclic Intermediates, V. - Asymmetric Synthesis of α-Methyl Amino Acids by Alkylation of the Lithiated Lactim Ether of cyclo-(L-Ala-L-Ala)

The (3S,6S)-2,5-dimethoxy-3,6-dimethyl-3,6-dihydropyrazine (7) is obtained from cyclo-(L-Ala-L-Ala) 5 (93-95percent optically pure) and trimethyloxonium tetrafluoroborate.With butyllithium the lithio derivative 8 is formed which reacts with alkyl halides in good chemical yields and with more than 90percent diastereoselectivity, whereby R-configuration is induced at C-3.A model concept is discussed, which explains the remarkably high asymmetric induction. - Hydrolysis (0.25 N HCl, room temp.) gives L-alanine methyl ester (4) and the (R)-α-methyl amino acid methyl esters 13.The two amino acid esters are separable by distillation or chromatography.