Protection of primary amines

The volume concludes with the preparation of four useful starting materials. The highly electrophilic tricarbonyl reagent DIMETHYL MESOXALATE finds application as a two-electron component in various pericyclic processes. 9-BROMO-9-PHENYL-FLUORENE is becoming increasingly used for the protection of primary amines, particularly amino acids and amino esters. Two methods for introducing the 9-phenylfluorenyl group are illustrated in the preparations of (S)-N-(9-PHENYLFLUOREN-9-YL)ALANINE AND (S)-DIMETHYL N-(9-PHENYLFLUOREN-9-YL)ASPARTATE. 

Protection of primary amines. Primary amines are selectively converted into mono-t-BDPSi derivatives by reaction with /-butyldiphenylchlorosilane and N(C2H,)3 in CH,CN. These derivatives are stable to basic and hydrolytic reagents as well as alkylating and acylating reagents such as CH,I and a base. They are cleaved by 80% HOAc at 25° or by Py-HF at 25°. 

The ability of [18]crown-6 derivatives to complex primary alkylammonium ions has been elegantly exploited in the protection of primary amines (80CC300). In the presence of primary amines, secondary amines can be acylated selectively by adding [18]crown-6 and a proton source. This strategy has obvious advantages over normal amine protecting groups which require a deprotection step. 

Protection of primary amines cf. 8, 437). I.aguzza and Ganem- recommend the diallyl derivatives for protection of primary amines. These compounds are prepared by reaction of the amine with allyl bromide and cthyldiisopropylaminc. Dc-protcction is accomplished by isomerization of the allyl groups to propenyl groups by Wilkinson s catalyst (5. 736) in refluxing aqueous acetonitrile. Under these conditions the resulting cnaminc is hydrolyzed with evolution of propionaldchyde, and llte amine is obtained in 65 90", yield. 

Protection of primary amines. Primary amines form the cyclic adducts 2 ("Stabasc adducts ) on reaction with I and a base (triethylamine for amines with pK 10 II, -butyllithium for less basic amines). The adducts are stable to n- and. KT-BuLi (-25°), LDA, H 0, CH3OH, KF, and NaHCOj but unstable to HOAc, HC1, KOH, and NaBH. ... 

Secondary amines do not generally form enamines with 2-acetyldimedone, and this protective group can therefore be used for the selective protection of primary amines in the presence of secondary amines [234,309], Support-bound 2-acetyldimedone has also been used as a linker for amines [312] (see Section 3.6). 

Figure 10.18. Protection of primary amines by tritylation [185,186]. (PS) MBHA polystyrene.

Selective protection of primary amines in the presence of secondary amines (e.g.. lysine), and monofunctionalizalion of symmetrical primary and secondary diamines, can be achieved. The trifluoroacylation of amines and amino acids by polymer-bound trifluoroacylation reagents has been described, with yields of 80-93%. °... 

PROTECTION OF PRIMARY AMINES 13.1.1. Using l,2-Bis(chlorodimethyIsilyl)ethane... 

Properties M.w. 232.52 b.p. 101-103 C (13 mm) Uses Difunctional blocking agent for the protection of primary amines Manuf./Distrib. Interchim http //WWW. interchim. com Trade Name Synonyms T1990 [United Chem. Tech, http //www.unitedchem.com]... 

Improved Synthesis of 2-Trimethylsilylethylsulfonyl Chloride. Vinyltrimethylsilane is converted in high yield in a straightforward fashion to 2-trimethylsilylethylsulfonyl chloride, an excellent organosilyl group for the protection of primary amines and in the formation of 2-trimethylsilylsulfonamides. The use of a 10-fold amount of DMF catalyst over that previously... 

For the protection of primary amines the succinoyl and phthaloyl groups may be introduced by heating a mixture of the amine and the acid anhydride to temperatures in the region... 

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