5-2,2,2-Trichloroethoxycarbonyl derivatives

Cleavage of fl-halourethanes. Eckert and Ugi have found that urethanes of this type can be cleaved to the amine by treatment with the anion of 1 in acetone or methanol at room temperature. The reaction involves alkylation followed by reductive fragmentation (equation I). The rate of cleavage depends on the structure of the blocking group 2,2,2-trichloroethoxycarbonyl derivatives (R = R = C1) are cleaved within 1-5 minutes. Cobalt(II) phthalocyanine (1) is recovered in almost quantitative yield in reusable form. 

A similar approach with pyridazine and 3-methylpyridazine, but using 1-trichloroethoxycarbonyl derivatives, allows the nucleophilic addition of thiazolones and 1,4-thiazinones (Scheme 16). The initial 1,4-dihydro adducts are oxidised and deacylated by treatment with sulfur in boiling DMF <87CPB2243, 90CPB45>. 

It has been reported that the reaction of NN-dimethylfuntumine (la) with trichloroethoxycarbonyl chloride gave the elimination product (2), in high yield, rather than the expected urethane (lb).4 Under the same reaction conditions the epimeric dimethylamino-pregnane derivatives (3a) and (3b) both gave the olefin (4), accompanied by minor amounts of the expected urethanes (3c) and (3d) respectively. The reaction of conessine (5a) with Cl3CCH2OCOCl yielded only the urethane (5b).4... 

Carboxylation. Bredereck s reagent has been used in a simple synthesis of L-y-carboxyglutamic acid (S), an unusual natural amino add present in prothrombin and believed to be involved in elotting. The starting material is the lactam 1 derived from L-glutamic acid and available commercially. It is converted by reaction with this reagent into the enamide 2. Reaction with 2,2,2-trichloroethoxycarbonyl chloride transforms 2 into the trichloroethyl ester 3 in moderate yield. The synthesis of 5 is completed by reaction with benzyl alcohol and triethylamine followed by hy drogenolysis. ... 

Due to the relatively high stability of the N-2,2,2-trichloroethoxycarbonyl (Troc) group to acids and its selective removal by zinc reduction even in the presence of Al-benzyloxy-carbonyl derivatives, it can offer interesting possibilities in the syntheses of particular pep-tidic compounds for example, it has been used for N -protection of lysine in the synthesis of The Af -Troc-protected lysine is readily prepared by reaction of the copper(II) complex with 2,2,2-trichloroethyl chloroformate (Troc-Cl)h d or by reaction of Z-Lys-OH (obtained via the benzylidene route, see Section 2.1.2.2.1.3) with 2,2,2-trichloroethyl chlor-oformate.f ... 

Trichloroethoxycarbonyl groups have been installed on primary and secondary hydroxyl groups of carbohydrate derivatives by standard coupling with 2,2,2-trichloroethyl chlorofor-mate. It has been shown that a Troc group in the primary position of a glycosyl donor reduces its reactivity but enhances a-selectivity in glycosylation couplings (O Scheme 46) [276]. 

Conversion of the N-acetyl phenylthioglycoside derivative 36 into die corresponding N- trichloroethoxycarbonyl (Troc) derivative 37 was described by Wu and Kiso using succinimidyl 2,2,2-trichloroethyl carbonate and trichloroethylchloroformate, respectively (Scheme 6). 

Among the groups studied, two led to good yields of sialylated lactosamine derivatives namely 2,5-dimethylpyrrole(2d) and trichloroethoxycarbonyl, Troc (27), cf. 31 and 32 Scheme 12. In our hands the donors prepared from 31 were not reactive with low nucleophilicity acceptors whereas 33 and 34 derived from 32 28)... 

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