43188-55-2

Upstream product

• 67-56-1 methanol 
• 43188-51-8 3(S)-hydroxy-2(S)-{[(4-methylphenyl)sulfonyl]amino}butanoic acid 
• 39994-75-7 (L)-allo-threonine methyl ester hydrochloride 
• 98-59-9 p-toluenesulfonyl chloride 
• 186581-53-3 diazomethane 

Downstream Products

• 637779-44-3 O-(2-anthracenoyl)-N-tosyl-(L)-allo-threonine 

Relevant academic research and scientific papers

Stereo- and regioselective synthesis of polysubstituted chiral 1,4-oxazepanes

The number of cyclic molecular scaffolds available to medicinal chemists remains limited, and simple structures such as oxazepanes are still made using multistep procedures, including a number of protection/deprotection steps and purifications. We report

Enantioselective Lewis Acid-Catalyzed Mukaiyama-Michael Reactions of Acyclic Enones. Catalysis by allo-Threonine-Derived Oxazaborolidinones

allo-Threonine-derived O-aroyl-B-phenyl-N-tosyl-1,3,2 -oxazaborolidin-5-ones 1g,n catalyze the asymmetric Mukaiyama-Michael reaction of acyclic enones with a trimethylsilyl ketene S,O-acetal in high enantioselectivity. A range of alkenyl methyl ketones is successfully employed as Michael acceptors affording ee values of 85-90% by using 10 mol % of the catalyst. The use of 2,6-diisopropylphenol and tert-butyl methyl ether as additives is found to be essential to achieve high enantioselectivity in these reactions. The effects of the additives are discussed in terms of the retardation of an Si+-catalyzed racemic pathway, which seriously deteriorates the enantioselectivity of asymmetric Mukaiyama-Michael reactions. A working model for asymmetric induction is proposed based on correlation between catalyst structures and enantioselectivities.

Synthesis of the four stereoisomeric forms of α,β diaminobutyric acid and some derivatives suitable for peptide synthesis

A synthetic route to the four stereo isomers of α,β diaminobutyric acid (α,β-A2bu) has been developed. The L threo, D threo, L erythro and D erythro isomers were prepared from the corresponding threonine and allo threonine isomers. N tosylation under Schotten Baumann conditions was followed by esterification with diazomethane and O tosylation in pyridine to give N,O ditosyl threonine methyl ester (IV). Successive treatments with ammonia saturated methanol and 6N HCl afforded, after several recrystallizations from water, N(α) tosyl α,β diaminobutyric acid (V) of the same configuration as the starting threonine along with racemic mixtures. Presumably, the sulfonamide moiety influenced the steric course of the reaction, causing a double inversion of the C(β) asymmetry center via intermediate aziridine formation. Simultaneous α,β elimination produced the accompanying racemic mixtures via 1 tosylaminocrotonic acid methyl ester. Removal of the tosyl group by the action of sodium in liquid ammonia gave α,β diaminobutyric acid (VI). The configurations of the four isomers were established by NMR and ORD spectra and by conversion of N(α) tosyl L threo α,β diaminobutyric acid (L threo V) to N tosyl L threonine (L threo II) through treatment with nitrous acid. The threo and erythro isomers of α,β A2bu (VI) and N(α) tosyl α,β A2bu (V) were further characterized by their elution behavior on ion exchange colum chromatography (amino acid analyzer) and by their ninhydrin color constants (C(HW)). The erythro isomers of α,β A2bu gave higher color constants (20.6) than the threo isomers (5.6 to 5.8). In the case of N(α) tosyl α,β A2bu, however, the threo isomers produced higher ninhydrin color values (11.3-11.4) than the erythro isomers (1.7 to 1.8). The NMR spectra (in DCl) of N(α) tosyl L threo α,β A2bu (L threo V) exhibited an H(α)-H(β) coupling constant (6.6 Hz) which is identical with that of the erythro isomers of the free amino acid (α,β A2bu). Several derivatives of L threo α,β diaminobutyric acid (L threo VI) suitable for use in peptide synthesis were prepared, including N(α) Tos N(β) Boc α,β A2bu, N(β) Boc α,β A2bu, N(α) Z N(β) Boc α,β A2bu, N(α) Z N(β) Boc α,β A2bu OMe, and N(α) Z α,β A2bu Ome x HCl.