84907-75-5

Upstream product

• 84907-70-0 1-((2R,5S)-5-Isopropyl-3,6-dimethoxy-2-methyl-2,5-dihydro-pyrazin-2-yl)-1-phenyl-ethanol 
• 28140-49-0 L-Val-D,L-Ala-OCH₃ 
• 15136-26-2 cyclo(L-Val-D,L-Ala) 
• 24601-74-9 (S)-4-isopropyloxazolidine-2,5-dione 
• 98-86-2 acetophenone 
• 72-18-4 L-valine 
• 98-88-4 benzoyl chloride 
• 914399-92-1 (6S)-6-isopropyl-5-methoxy-3-methyl-3,6-dihydro-2-pyrazinyl methyl ether 
• 115228-42-7 (2S,5S)-2-benzoyl-2,5-dihydro-5-isopropyl-3,6-dimethoxy-2-methylpyrazine 
• 19493-09-5 Methylenetriphenylphosphorane 

Downstream Products

• 4070-48-8 L-Valine methyl ester 
• 84907-73-3 (R)-α-(1-phenylethenyl)alanine methyl ester 

Relevant academic research and scientific papers

Asymmetric Syntheses via Heterocyclic Intermediates, XL. - Studies on the Acylation of Lithiated Bislactim Ethers of cyclo(-L-Val-Ala-) and cyclo(-L-Val-Gly-). - Asymmetric Synthesis of (R)-α-Alkenyl and (R)-α-Ethinyl Alanine Methyl Esters by the Bislactim Ether Method

The lithiated bislactim ether 2a of cyclo(-L-Val-Ala-) reacts with acyl chlorides 3 highly diastereoselectively to yield the compounds 4 with (2S,5S)-configuration.With acetyl chloride (3a) the N-acetyl compound 7 is formed as a sideproduct.Alternatively, the compounds 4 can be obtained by oxidation of the carbinols 8.From 4a and b, the olefins 11a and b are obtained by Wittig reaction.These are precursors of methyl (R)-α-alkenyl alanine methyl esters of type 13. (R)-α-ethinyl alanine methyl ester 17 is obtainable from 4a and 4e via the intermediates 14 or 15 and16a.The lithiated bislactim ether 2c of cyclo(-L-Val-Gly-) reacts with benzoyl chloride (3b) to give the "bis adduct" 18.However, 6b is obtained from 2c and the benzamide 19, though as a 1:1 diastereomeric mixture.Presumably, 6b epimerizes via the enol 21a subsequently to its diastereoselective formation.

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.