Terf-butoxycarbonylation

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... 

This category is exemplified, albeit poorly, in the reaction of 3-methyl-1,2-benzenediamine (405) with tri-terf-butyl 2-hydroxy-3-oxo-l,2,5-pyrrolidinetricar-boxylate (406) in aqueous ethanolic sodium hydrogen carbonate under reflux for 3 h. This gave, as minor products, an inseparable mixture (in 9% yield) of tert-butyl 3-[2-(terf-butoxycarbonyl)-2-(ferf-butoxycarbonylamino)ethyl]-5-methyl-2-quinoxalmecarboxylate (407, Q = Me, R = H) and its 8-methyl isomer (407, Q = H, R = Me)276... 

N-(terf-butoxycarbonyl)-N-(tert-butoxycarbonyl)-, benzyl ester glycyl-L-alanine-, methyl ester... 

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). 

Principle of the terf-Butoxycarbonyl/Benzyl/Phenacyl Strategy... 

Azetidine-2-carboxylic acid (2) like proline gives an intense blue color with sodium nitroprusside in 10% acetaldehyde solution in the presence of sodium carbonate. 98,99 Upon usual acid hydrolysis (6M HC1, 110 °C, 24 h or more) as required for amino acid analysis, azetidine-2-carboxylic acid is completely decomposed, yielding mainly homoserine lactone, as well as other ninhydrin-positive compounds. 87,89,99 To enable an accurate quantification of this imino acid, azetidine-2-carboxylic acid peptides should be hydrolyzed by alkali (5M barium hydroxide, at 100 °C for 18 h 89 or 2 M sodium hydroxide at 110°C for 22h 100 ). There are extensive NMR spectroscopic data available 100-104 and the absolute configurations of A-acetyl-L-azetidine-2-carboxylic acid 105 and A-terf-butoxycarbonyl-L-azetidine-2-car-boxylic acid 106 have been determined by X-ray analysis. 

Methyl (9S,12S>12-[(terf-Butoxycarbonyl)(niethyl)amino]-4-nitro-ll-oxo-2-oxa-10-azatricyclo[12J.2.13-7]-nonadeca-l(16),3(19),4,6,14,17-hexaene-9-carboxylate (25) [251... 

S, 8aS )-6-[(terf-Butoxycarbonyl)aminol-5-oxohexahydro-5H-thiazolo[3,2-a]pyridine-3-carboxylic Add (31) [77]... 

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. 

Bromocyclocarbamation reaction of 2-allyl-l-(terf-butoxycarbonyl)tetra-hydropyridine 94 gave inseparable mixture of 3-epimers of 95 and 96. When a bulky R1 substituent ((Bu) was present in 94 a good level of diastereoselectivity was observed (07EJ02015). Reaction of 2,6-diallyl-tet-rahydropyridine 97 with Boc20, followed by bromocyclocarbamation reaction with NBS, then the treatment of the reaction mixture with KOfBu yielded a mixture of 5- and 7-bromo-3-methylene-tetrahydro-lH-pyrido[l,2-c][l,3]oxazin-l-ones 98 and 99. 

Acquired immune deficiency syndrome 10.1 0 -/h.v 3-carboxypropvl -9.9 -biacridinium dinitrate /i/.vguanidinium tren-cholesterol terf-Butoxycarbonyl... 

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. 

SCHEME 12.21 Synthesis of the glycan moiety of HPG-7. Boc, terf-butoxycarbonyl. 

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 reaction of N-(terf-butoxycarbonyl)leucinal 2-41 a by Danishefsky et al. with l-methoxy-3-trimethylsilyloxy-l,3-butadiene 2-10 gave the pyrones 2-42 and 2-43 with an induced diastereoselectivity of 9 1 in favour of the syn-com-pound in the presence of Eu(hfc)3 [96]. Later Garner [97] used a N-Boc-serine derived aldehyde 2-41 b and Danishefsky s diene 2-10. In both cases a chelation-control forming a complex between the nitrogen and the oxygen could explain the obtained selectivity. In the presence of HMPA chelation is minimized to give a higher extent of the anfi-product 2-43 (Fig. 2-12) [97]. 

A highly reactive guanidinylating reagent has also been proposed with the traceless reagent derived from l-(terf-butoxycarbonyl)-2-triflylguanidine which is linked at N3 via a benzyloxycarbonyl moiety to the resin.h ... 

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