Trichloroethoxycarbonyl group

Treatment of A - -butyl-2,3,9,10-tetrahydrolysergamide 7a with elemental bromine or pyridinium bromide perbro-mide failed to yield a well-defined product. However, when the basic nitrogen at position 1 of 7a was masked with an acetyl (13) or 2,2,2-trichloroethoxycarbonyl group (14), bromination proceeded smoothly to yield the 12-bromo compounds 15 and 16, respectively. Removal of the labile protecting group14 from 16 afforded 17. 

The 2,2,2-trichloroethoxycarbonyl group is stable to acid, but somewhat labile to base. A superior protective group is the 2,2,2-trichloro-t-butyloxycarbonyl group, which is stable to both acid and base. The group is introduced by means of the stable chloroformate, prepared from chloretone (equation II). This protecting group is cleaved by the anion 2 in about 1 minute in approximately 90% yield. It is also... 

This can be used during the preparation of unsaturated 1,2- and 2,3-diacyl-5n-glycerols. The 2,2,2-trichloroethoxycarbonyl group is introduced on to the free primary hydroxyl group as the carbonyl chloride. It is retained, without migration, when the isopropylidene group is removed and is, itself, removed with zinc in acetic acid at room temperature (Pfeiffer era/., 1968). 

The carbobenzoxy group, which has been widely used in the protection of amino functions in peptide chemistry [100], has also been used to protect alcoholic functions [101]. Recently, the use of the 2,2,2-trichloroethoxycarbonyl group has been reported [102]. Alcohols react with 2,2,2-trichloroethyl chloro-... 

The reactions described so far all yield medium-ring tertiary amines. Reinecke s group have recently extended their methods to synthesize the more useful secondary amines.288 Three syntheses were developed. The first [Eq. (31)] involves reductive cleavage of the benzyl indolizidinium salt 229 with lithium aluminum hydride, followed by replacement of the benzyl group with the labile trichloroethoxycarbonyl group. The latter may be removed under mild conditions with zinc-methanol, which does not cause migration of the double bond. 

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]. 

The j3,/8,j3-trichloroethoxycarbonyl group has proved useful in the synthesis of optically active 1,2-diacylglycerols (5).1 Thus 1,2-isopropylidene-sn-glycerol (1) is treated with /3,/3,/3-trichloroethyl chloroformate and pyridine in dry chloroform. The isopropylidene group of the product (2) is then cleaved with dilute hydrochloric acid to give sn-glycerol-3-j8,/3,)3-trichloroethylcarbonate (3). This is then acylated with an acyl chloride (pyridine-chloroform) (4) and in the fined step the protective group is cleaved with activated zinc in acetic acid.2... 

Amino nitroxides. The )3,, )3-trichloroethoxycarbonyl group was used for protection of the less hindered amino group of (1) during oxidation of the more hindered amino group to a nitroxide. ... 

Trichloroethoxycarbonyl group, use as protective group, 294 Tricosanoic acid, 1,169,350 Tridecanoic acid, 1,350,351 Tridocosahexaenoin, 133 Triesters in waxes, 143 Triglycerides, see Triacylglycerols Trihydroxystearic acids, 21, 462 Trilaurin, 369, 372, 373, 375 Trimargarin, 368... 

Recently, Iwao reported (57) the dehydrative cyclization of 119 in the total synthesis of /-clavicipitic acid. Iwao prepared the diester 118, having protected the amino group with a trichloroethoxycarbonyl group, which was then readily cleaved by treatment with zinc dust to recover the free amine 119 in... 

A Paquet. Introduction of 9-fluorenylmethoxycarbonyl, trichloroethoxycarbonyl, and benzyloxycarbonyl amino protecting groups into O-unprotected hydroxyamino acids using succinimidyl carbonates. Can J Chem 60, 976, 1982. 

The silyl protective groups on the baccatin core structure were removed under reaction conditions. Bac3 Pi = H, P2 = Bz, P4 = Ac, P7 = Pio = 2,2,2-trichloroethoxycarbonyl. 

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