- New and Effective Routes to Fluoro Analogues of Aliphatic and Aromatic Amino Acids
-
New and efficient syntheses of 4,4,4-trifluorovaline (1), 5,5,5-trifluoronorvaline (2), 5,5,5-trifluoroleucine (5), 6,6,6-trifluoronorleucine (6), 4,5,6,7-tetrafluorotryptophan (25), and α-(trifluoromethyl)-β-alanine are studied.Trifluorovaline (1) and trifluoronorvaline (2) are synthesized through amidocarbonylation of 2-(trifluoromethyl)propanal (2-TFMPA) and 3-(trifluoromethyl)propanal (3-TFMPA), respectively, followed by hydrolysis.Trifluoroleucine (5) and trifluoronorleucine (6) are synthesized by using modified Erlenmeyer's azlactone method from 2-TFMPA and 3-TFMPA, respectively. (S)- and (R)-trifluoronorvalines and trifluoronorleucines with high enantiomeric purities (95-100percent ee) are obtained through enzymatic optical resolution of N-acetyltrifluoronorvaline (4) and N-acetyltrifluoronorleucine (17) with the use of a porcine kidney acylase I.Optically active trifluoronorleucine is also obtained via the asymmetric hydrogenation of (Z)-N-benzoyldehydrotrifluoroleucine ethyl ester (10a-Z) with a chiral rhodium catalyst, ClO4, followed by hydrolysis.Unexpectedly high diastereoselectivities (80-87percent ee) are observed in the hydrogenation of (Z)-N-benzoyldehydrotrifluoroleucine ethyl ester (11b) and (Z)-N-benzoyl-4-(pentafluorophenyl)dehydronorvaline (14-Z) over palladium/carbon. 4,5,6,7-Tetrafluorotryptophan (25) and 4,5,6,7-tetrahydrotryptamine (30) are synthesized from 3-formyl-4,5,6,7-tetrafluoroindole (22a) in 51percent (four steps) and 83percent (two steps) overall yields, respectively. 4,5,6,7-Tetrafluoroindoleacetic acid (28) is obtained from 1-acetyl-3-(acetoxymethyl)-4,5,6,7-tetrafluoroindole (23a) in four steps in 65percent overall yield.The 3-formyl- and 1-acetyl-3-(acetoxymethyl)tetrafluoroindoles (22a, 23a) are prepared through selenium dioxide oxidation of 1-acyl-3-methyl-4,5,6,7-tetrafluoroindole (21), which is obtained via the cyclization of a Schiff base of 2-(pentafluorophenyl)propanal (2-PFPPA), in good yields.
- Ojima, Iwao,Kato, Koji,Nakahashi, Kazuaki,Fuchikami, Takamasa,Fujita, Makoto
-
p. 4511 - 4522
(2007/10/02)
-
- Polyfluoroaralkyl amines. Further studies on the reactivity of 4,5,6,7-tetrafluoroindole
-
4,5,6,7-tetrafluoroindole 1 undergoes electrophilic formylation and aminoalkylation at C-3 to give compounds that can be readily converted to a variety of products, including the skatole, tryptamine, and tryptophan. 1 reacts with ethyl diazoacetate to yield 4,5,6,7-tetrafluoroethyl-3-indole acetate.The Grignard reagent of 1 offers a direct route to the versatile substituted acetonitrile 10 via C-3 alkylation with chloroacetonitrile.Key words: tetrafluoroindole, tetrafluorotryptamine, tetrafluoroindolyl magnesium bromide, tetrafluorotryptophan.
- Filler, Robert,Woods, Sarah M.,White, William L.
-
p. 1837 - 1841
(2007/10/02)
-
- SELENIUM DIOXIDE OXIDATION OF 3-METHYL-4,5,6,7-TETRAFLUOROINDOLES: AN EFFICIENT ROUTE TO TETRAFLUORO ANALOGS OF 3-FORMYL AND 3-ACETOXYMETHYLINDOLE SYSTEMS
-
Selenium dioxide oxidations of 3-methyl-4,5,6,7-tetrafluoroindoles gave 3-formyl or 3-acetoxymethyltetrafluoroindoles in unexpectedly high selectivities, which turned out to serve as useful intermediates for the syntheses of tetrafluoro analogs of tryptop
- Fujita, Makoto,Ojima, Iwao
-
p. 4573 - 4576
(2007/10/02)
-
