N-Ethylamino acid synthesis and N-acylamino acid cleavage using Meerwein's reagent

Abstract

N-Ethylamino acids have been prepared by reaction of N-acetylamino acids with trimethyloxonium tetrafluoroborate (Meerwein's reagent) giving imino ether fluoroborates, followed by reduction with sodium borohydride. The use of Meerwein's reagent for the deacylation of N-acylamino and N-acyl, N-methylamino acid derivatives has been investigated.

Synthesis of N‐Alkyl Amino Acids

“…Although the reduction of amino acid amides to N-alkyl amino acids [66][67][68], diverges from the parent topic title of Schiff s base reductions, its inclusion in this section is warranted due to its similarity with borohydride reductions of imine intermediates. Krishnamurthy [67] made use of the selective reduction of various formanilides and some alkyl formamides with excess borane/dimethylsulfide complex (BH 3 ÁSMe 2 ).…”

“…Chen and Benoiton [66] have also devised a mild room temperature reduction of acetamides using Meerweins reagent [108] (trimethyloxonium tetrafluoroborate, Scheme 6.44). By treating the acetamides with trimethyloxonium tetrafluoroborate an imino ether fluoroborate intermediate 120 forms that is reduced to the alkyl substituent with sodium borohydride.…”

Synthesis of New N‐Ethyl Dehydroamino Acid Derivatives: N‐Ethyl β,β‐Dibromo, N‐Ethyl β‐Bromo β‐Substituted, and N‐Ethyl β,β‐Disubstituted N‐Protected Dehydroamino Acid Methyl Esters

“…Fewer methods for the synthesis of N ‐ethylated amino acids and their derivatives are available in the literature 5. Chen and Benoiton prepared N ‐ethyl amino acids by reaction of N ‐acetyl amino acids with trimethyloxonium tetrafluoroborate (Meerwein's reagent) in a two‐step procedure 6. Initially, an imino ether fluoroborate is formed and then reduced by treatment with sodium borohydride.…”

N‐(4‐Nitrophenylsulfonyl)‐ and N‐(Fluorenylmethoxycarbonyl)‐N‐ethyl Amino Acid Methyl Esters – A Practical Approach

“…[14] An alternative route for the synthesis of N-ethyl amino acids was provided by the reduction of O-alkyl acetohydroxamate obtained from amino acids. [15] Another approach describes the N-ethylation of carbobenzyloxy (Z)-and tert-butoxycarbonyl (Boc)-protected amino acids by starting from the generation of a dianion derivative at the oxygen and nitrogen atoms that is subsequently alkylated with ethyl iodide. [16] However, Hansen and co-workers [17] suggest that this procedure affords only a trace of ethylated product because a β-elimination reaction of the alkylating agent preferentially occurs.…”