ChemInform Abstract: tert‐Butyloxycarbonyl‐ and Benzyloxycarbonylamino Acid Fluorides. New, Stable Rapid‐Acting Acylating Agents for Peptide Synthesis.

Abstract

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Amino acid fluorides: viable tools for synthesis of peptides, peptidomimetics and enantiopure heterocycles

“…Bsmoc (51; Table 3), 36,37 Bspoc (52; Fig. 8) 37,38 and Mspoc (53; Fig. 8) 39 protected amino acid uorides with base labile sulfonyl-based N-protecting groups have also been reported using cyanuric uoride.…”

“…9). 38 3.4 C a,a -dialkyl and N-methyl amino acid uorides A list of C a,a -dialkyl and N-methyl amino acid uorides is given in Table 4 and these were prepared by similar methods to those described previously and have been utilized successfully in sterically hindered coupling.…”

“…Furthermore, Bsmoc-Leu-Leu-Leu-OFm (Fm ¼ 9-uorenylmethyl; yield ¼ 67.4%), Bsmoc-Leu-Phe-OFm (73.4%) 37 and the synthesis of [Leu 5 ]enkephalin using Mspoc-amino acid uorides were also demonstrated using this method. 38 4.1.4 Other coupling protocols. Fmoc-amino acid uorides can be coupled in the absence of base and even more effectively by silylation of the amine component using a silylating agent such as N,O-bis(trimethylsilyl)acetamide (BSA).…”

“…Within a short period of time, many more classes of acid uorides were prepared from non-proteinogenic amino acids such as a,a-disubstituted ones {a-aminoisobutyric acid (Aib), isovaline (Iva), a-ethylalanine, [31][32][33] a,a-diethylglycine (Deg), a,a-dibutylglycine and 1-aminocyclopentane-1-carboxylic acid (Ac 5 c), 1-aminocyclohexane-1-carboxylic acid (Ac 6 c), 1aminocycloheptane-1-carboxylic acid (Ac 7 c)}, 34 N-methylated (NMe) amino acids including NMe alanine (Ala), NMe leucine (Leu), NMe valine (Val), sarcosine (Sar or N-methylglycine) 34 and N-methylated C a,a -dimethylamino acids such as NMeAib}. 35 Other new N-urethane protecting groups such as 1,1-dioxobenzo [b]thiophene-2-ylmethyloxycarbonyl (Bsmoc) namely Bsmoc-Asn(Trt)-F, Bsmoc-Asn(Dmcp)-F (Asn ¼ asparagine; Dmcp ¼ dimethylcyclopropylmethyl Gln ¼ glutamine), Bsmoc-Gln(Trt)-F, Bsmoc-Gln(Dmcp)-F), 36,37 2-(tert-butylsulfonyl)-2propyloxycarbonyl (Bspoc), 37,38 2-methylsulfonyl-3-phenyl-1prop-2-enyloxycarbonyl (Mspoc) 39 and non-urethane types including the Trt group 40 were also employed as N-protecting groups for the preparation of amino acid uorides.…”