Trifluoroacetyl protection

For modified nucleosides bearing trifluoroacetyl-protected amino groups, after step 3 of Protocol 10, add one volume of 33% aqueous ammonia solution to the reaction and stir at room temperature overnight. Then evaporate the solution to an oil, redissolve in 50 mM TEAB and purify by MPLC according to Protocol 19. 

Complexation of dihydronaphthalene with chromium tricarbonyl facilitates the attack of a nucleophilic amine and stereoselectively directs the protonation "anti" to the metal atom. (+)-(l S,2 R)-, 2-Dihydro-7-methoxy-1,4-dimethyl-1 - 2 -[methyl(trifiuoroacetyl)amino]propyl -naphthalene [(+)-7] was treated with chromium hexacarbonyl to give a mixture of a- and /(-chromium tricarbonyl complexes in a 10 1 ratio ( H NMR). The complexes were separated and the a-isomer cyclized by base treatment and sonication. Dccomplexation gave the ben-zomorphan tricycle 8 in low yield [40%, based on recovered (+)-7]18. The trifluoroacetyl protection of the amino group was necessary to achieve both stereoselective complexation with chromium tricarbonyl and successful cyclization. 

Trifluoroacetylations. Protection of amines (11 examples, 85-100%) and alcohols (7 examples, 54-95%, including phenols) is achieved with this reagent at room temperature. 

Peptide synthesis. The reagent is used to prepare N-trifluoroacetyl derivatives of amino acids and peptides. The substrate is warmed with 1.2-2 equivalents of the reagent in molten phenol at 120-150° for 2-20 min. Excess reagent and phenol are removed under vacuum or by solution in petroleum ether or carbon tetrachloride, from which the amino acid derivative crystallizes. The main advantage of the N-trifluoroacetyl protective group is that it can be removed under very mild conditions. 1,. Benoiton, H. N. Rydon, andJ. E. Willett, Chem. Ind., 1060(1960)... 

As shown in Scheme 36, a Heck polyannulation reaction was realized between dibromo(indolyl)maleimide 209 and diacetylenyl trifluoroacetanilide 210 to assemble indolo[2.3-a]carbazole 211, the Af-prolecied aglycone of rebeccamycin (25). Four bonds were formed in one step from a single monocyclic 1,3-diacetylene precursor [101] and the trifluoroacetyl protecting groups were readily cleaved during the workup. 

Trifluoroacetyl protecting group, 135, 254 Triglycolic acid, JV.iV -biscarbonylimidazole derivative, 112... 

Acetal 136 on enolization followed by conjugate addition with nitro olefin 122 gave alkylated products 137 and 138 in a diastereomeric mixture of 10 1. Compound 137 was proceeded for amathaspiramide F synthesis, which on hydrolysis followed by N-trifluoroacetyl protection gave amide 139. Nitro group of compound 139 was converted into oxime 140. Hydrolysis of oxime followed by cyclization and then deprotection of N-trifluoroacetyl group gave amathaspiramide F (134) Scheme 12 [63],... 

Although many of the anilines used in the Sandmeyer isatin synthesis have minimal functionality, examples exist where potentially sensitive motifs can survive the harsh reaction conditions. The 6-azauracil substituted aniline 39 could be converted to isatin 40 en route to the polyheterocyclic compound 41. A trifluoroacetyl protected amine could also be carried through the two-step Sandmeyer sequence to yield the isatin of interest. ... 

The final step in the synthesis of the target molecule, sulfanilamide, is the conversion of the sulfonyl chloride intermediate to a sulfonamide and the removal of the 2,2,2-trifluoroacetyl protecting group. These transformations are accomplished in one step because both reactions take place upon heating the protected sulfonyl chloride with aqueous ammonia. The reaction sequence is shown here ... 

For our specific synthesis, the allyl ester substrate for the Ireland-Claisen 1 was obtained in a 78% yield through a l-ethyl-3-(3-dimethylaniinopropyl) carbodiimide (EDC) coupling reaction between a trifluoroacetyl-protected glycine and allyl alcohol (Scheme 2). Reaction conditions discovered by Kazmaier were then used to perform the Ireland-Claisen reaction and... 

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