181137-46-2

Upstream product

• 181137-45-1 (2R,3S)-2-Hydroxy-3-(toluene-4-sulfonylamino)-decanoic acid ethyl ester 
• 162518-06-1 (R)-4-methyl-N-(5-oxotetrahydrofuran-3-yl)benzenesulfonamide 
• 162601-64-1 (2R,3S)-2-hydroxy-3-(tosylamino)butano-4-lactone 
• 162518-07-2 ethyl (2R,3R)-3-<(N-tosyl)amino>-2-hydroxy-4-iodobutyrate 

Relevant academic research and scientific papers

104. The enantioselective synthesis of β-amino acids, their α-hydroxy derivatives, and the N-terminal components of bestatin and microginin

L-Aspartic acid by tosylation, anhydride formation, and reduction with NaBH4 was converted into (3S)-3-(tosylamino)butan-4-olide (8; Scheme 1). Treatment of 8 with ethanolic trimethylsilyl iodide gave the N-protected deoxy-iodo-β-homoserine ethyl ester 9. The latter, on successive nucleophilic displacement with lithium dialkylcuprates (→ 10a-e), alkaline hydrolysis (→ 11a-e), and reductive removal of the tosyl group, produced the corresponding 4-substituted (3R)-3-aminobutanoic acids 12a-e (ee >99%). Electrophilic hydroxylation of 8 (→ 19; Scheme 3), subsequent iodo-esterification (→ 21; Scheme 4), and nucleophilic alkylation and phenylation afforded, after saponification and deprotection, a series of 4-substituted (2S,3A)-3-amino-2-hydroxybutanoic acids 24 including the N-terminal acids 24e (= 3) and 24f (= 4) of bestatin and microginin (de >95%), respectively.