84907-85-7

Upstream product

• 84907-82-4 (3R,6S)-3,6-Dihydro-3-(1-hydroxy-1-methylethyl)-6-isopropyl-2,5-dimethoxypyrazin 
• 87378-22-1 (3R,6S)-3,6-Dihydro-3-(1-hydroxy-1-methylethyl)-6-isobutyl-2,5-dimethoxypyrazin 

Downstream Products

• 2280-48-0 (R)-(-)-β-hydroxyvaline 
• 1363373-90-3 C₂₃H₂₂N₂O₄ 

Relevant academic research and scientific papers

Asymmetric Syntheses via Heterocyclic Intermediates, XVIII. - On the Enantioselective Synthesis of (2R)-Serine Methyl Esters or (2R)-Serines Starting with the Bis(lactim) Ether of cyclo-(-L-Val-Gly)

The lithiated bis(lactim) ether 8a furnishes with aldehydes and ketones in good yields the addition products 11 with (3R) configuration.The asymmetric inductions at C-3 of 11 (d.e. values) amount to more than 95 percent with ketones, with aldehydes they are somewhat smaller.With unsymmetrical ketones or aldehydes C-3' also becomes a chiral center.For the (3R)-major diastereomers the "second induction" at C-3' varies from about 4 t about 87 percent (for benzaldehyde or isobutyraldehyde, respectively), preferably the (3R,3'S) epimers are formed. - Acid hydrolysis of 11 yields (besides methyl L-valinate) the (2R)-serine methyl esters 26.Their e.e. values correspond with the d.e. values of 11. - Dehydratation of 11 furnishes the "Hofmann olefins" 32 and/or the "Saytzeff olefins" 33 which can be transformed in various ways into optically active amino acids.

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.