Terf-Butoxycarbonyl-protected

Denkewalter et al. 4 synthesized a series of terf-butoxycarbonyl-protected poly(a,e-L-lysine) macromolecules (see above, Scheme 4.3), whose molecular models suggested them to be globular, dense spheres and whose molecular weight distribution was determined to be very narrow (MJM = 1.0). Since each generation in this series was synthesized in a stepwise manner, each member was predicted to have a monodisperse molecular weight. 

The synthesis of these inhibitors is not always straightforward because some hydro-xybenzyl derivatives that have very good leaving groups (like their aminobenzyl analogues) are unstable. Hence, more stable precursors are often used, such as phenyl ethers30-32 or silyl ethers.33-35 Other functional groups present in the molecule must be sometimes protected (/V-terf-butoxycarbonylation of amides for example).36,37... 

Examples are given in Table 4—1 for the synthesis of amides of AT-protected amino acids by means of imidazolides and triazolides (where Z and Boc represent the protecting groups benzyloxycarbonyl and terf-butoxycarbonyl) ... 

In the final stage, as depicted in Scheme 10, the BOC-protected compound 45 and the quinolone carboxylic acid 27 are heated in DMSO under tri-ethylamine, followed by deprotection of the terf-butoxycarbonyl group under acidic condition to afford the final product DQ-113 (26). 

The most common reagent for introducing the terf-butoxycarbonyl (Boc) protecting group is the pyrocarbonate B0C2O. This is employed here in aqueous alkaline medium to which has been added the solubilizing agent dioxane. 

The terf-butoxycarbonyl (BOC) group is used to protect the amino group of an amino acid during protein synthesis in the laboratory. The BOC group is attached to the amine by this reaction ... 

The BOC derivative of phenols can be prepared using a phase transfer protocol (BOC2O, BU4NHSO4 or 18-crown-6, NaOH, CH2CI2, 80% yield) or by direct acylation with BOC2O and DMAP as a catalyst (79-100% yield) The unusual process of protecting a phenol in the presence of the more nucleophilic amine has been accomplished with l-terf-butoxy-terf-butoxycarbonyl-l,2-dihydroquinoline. Chemoselec-tivity is controlled by the solvent. 

The synthesis of glycopeptides of L-asparagine by the solid-phase procedure required a derivative protected, for example, by the acid-labile N-(ferf-butoxycarbonyl) group. Thus, 1-benzyl N-(terf-butoxycarbonyl)-L-aspartate (88) was condensed with 2,3,4,6-tetra-0-acetyl-)3-D-gluco-pyranosylamine (2), or the 2-acetamido-2-deoxy analog 8, by the active ester method in the presence of DCC and 1-hydroxybenzotriazole, to give 89 and 90, respectively ... 

The alkoxycarbonyl protecting groups can also be introduced into amines by, triazolides (Table 4—7). With A-tert-butoxycarbonyl-1,2,4-triazole the tert-butoxy-carbonyl protecting group (Boc) is transferred readily onto amino functions of primary amines, trimethylbenzyl ammonium salts of amino acids, or peptides.[ 1965 Alternatively, the Boc group can be transferred with terf-butylphenylcarbonate in the presence of 1,2,4-triazole. In this latter approach the triazolide is presumably formed as an intermediate. ... 

FIGURE 3.17 Reagents for protection of amino groups as the ferf-butoxycarbonyl derivatives. terf-Butyl chloroformate is rarely used because of its low boiling point. The oxime is 2-ferf-butoxycarbonyloximino-2-phenylacetonitrile,45 Boc20 = di-ferf-butyl dicarbonate, or di-terf-butyl pyrocarbonate.46 (Tarbell et al., 1972 Pozdvev, 1974). Acylations are carried out at pH 9 to avoid dimerization. 

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