Benzyl Chloroformate related reagents

For further variations of the Z group and related properties see Table 2 and previous reviews on this subject.t 1 Most of these protecting groups are introduced by procedures similar to those described for the synthesis of N-Z derivatives, either with the corresponding chloroformates, azido formates or mixed carbonates. However, these reagents are usually not commercially available, except for 4,5-methoxy-2-nitrobenzyl chloroformate, 4-nitro-benzyl chloroformate, and the 4-methoxybenzyl carbazate [Z(OMe)-NHNH2] as precursor of Z(OMe)-N3. 

The difficult preparation of Z-Arg(Z)2-OH, and thus the related low yields associated with earlier methods,f l are conveniently bypassed if persilylated A -(benzyloxy-carbonyl)arginine is acylated with benzyl chloroformate.f 1 This procedure is also well-suited for the preparation of Boc-Arg(Z)2-OH.P l Alternatively, the N -bis-protected derivatives are also obtained in good yields via guanidinylation of N -protected ornithine with N,N -bis-protected guanidinylating reagents (see Section 2.6.1.6).t l For peptide acylation steps, both Z-Arg(Z)2-OH and Boc-Arg(Z)2-OH are mainly used as active esters,f l mixed anhydrides or carbodiimides.P l... 

A related reagent to PhI(OAc)2 and PhI(02CCF3)2 is [hydroxy(tosyloxy)iodo]benzene (Phl(OH)OTs), which has the advantage over PhI(02CCp3)2 of improved stability and which is especially useful for the HR of long-chain primary amides." A similar HR reagent is [methoxy(tosyloxy)iodo]benzene (Phl(OMe)OTs), which has increased solubility in acetonitrile over that of PhI(OH)OTs." Examples of these HR transformations are given here (41 —> 42 and 43 —> 44 —> 45)." " Intermediate 44 could be isolated and characterized, and when it is heated in chloroform, the expected benzyl isocyanate is isolated." ... 

Related Reagents. Allyl Chloroformate Benzyl Chlo-roformate 4-Bromobenzyl Chloroformate t-Butyl Azidoformate l-(t-Butoxycarbonyl)-lEf-benzotriazole 3-A-oxide 1 -(r-Butoxycarbonyl)imidazole 2-(t-Butoxycarbonyloxyimino)-2-phenylacetonitrile A-(t-Butoxycarbonyloxy)phthalimide A-(t-Butoxycarbonyloxy)succinimide V-(r-Butoxycarbonyl)-1,2,4-triazole Di-t-butyl Dicarbonate Ethyl Chloroformate 9-Fluorenylmethyl Chloroformate Isobutyl Chloroformate Methyl Chloroformate 2,2,2-Tribromoethyl Chloroformate 2,2,2-Trichloroethyl Chloroformate 2,2,2-Trichloro-t-butoxycarbonyl Chloride 2-(Trimethylsilyl)ethyl Chloroformate Vinyl Chloroformate. 

Related Reagents. Allyl Chloroformate Benzyl Chloroformate 4-Bromobenzyl Chloroformate f-Butyl Chloroformate Ethyl Chloroformate Isobutyl Chloroformate Methyl Chloroformate 2,2,2-Tribromoethyl Chloroformate 2,2,2-Trichloro-f-butoxycarbonyl Chloride 2,2,2-Trichloroethyl Chloroformate 2-(Trimethylsilyl)ethyl Chloroformate Vinyl Chloroformate. 

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