BULLETIN OF THE
Note
KOREAN CHEMICAL SOCIETY
1
B. Joseph, Curr. Org. Chem. 2001, 5, 471, and references
therein; (c) F. Popowycz, S. Routier, B. Joseph, J. Y. Merour,
Tetrahedron 2007, 63, 1031; (d) F. Popowycz, J. Y. Merour,
B. Joseph, Tetrahedron 2007, 63, 8689.
product was obtained in 80% yield as an oil. H NMR (200
MHz, CDCl3) δ 4.05 (m, 5H), 3.87 (t, 1H, J = 3.4 Hz), 2.63
(m, 2H), 2.20 (m, 1H), 1.19 (m, 6H), 0.95 (d, 3H, J = 6.9
Hz), 0.61 (d, 3H, J = 6.8 Hz), 0.10 (s, 9H); 13C NMR (100
MHz, CDCl3) δ 164.3, 161.2, 103.6. 86.6, 61.0, 60.8, 60.7,
54,6 31.6, 26.6, 19.2, 16.7, 14.8, 14.4, 0.4; MS (EI) m/e (rel.
intensity) 322 (M+, 13), 294(8), 279 (13) 211 (74), 169 (100).
1-Benzyl-2-trimethylsilyl-azatryptophan ethyl ester (7)
(3R,6S)-3-[1-Benzyl-2-trimethylsilyl-3-azaindolyl]
2. I. Jeanty, F. Suzenet, G. Guillaument, J. Org. Chem. 2008, 73,
7390 , and references therein.
3. M. M. Robinson, B. L. Robinson, J. Am. Chem. Soc. 1955,
77, 457.
4. F. Crestey, V. Collot, S. Stiebing, J.-F. Lohier, J. S. Oliverira
Santos, S. Rault, Tetrahedron Lett. 2007, 48, 2457, and refer-
ences therein.
5. (a) A. R. Offenbacher, C. V. Pagba, B. C. Polander, U. Brahma-
chari, B. A. Barry, ACS Chem. Biol. 2014, 9, 891 , and references
therein; (b) M. G. Hoesl, M. Larregola, H. Cui, N. J. Budisa,
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methyl-2,6-dihydro-6-isopropyl-2,5-diethoxypyrazine (251
mg, 0.5 mmol) was dissolved in THF (20 mL). The optically
activesolutionwascooledat−78 ꢀCandslowlyaddedtoasolu-
tion of aqueous 2 N HCl (aq. 12 N HCl: ethanol = 1: 5). The
mixturewasallowedtowarmto0 ꢀCandstirredfor2h. Twenty
milliliters of ice water was added to the solution, and pH of the
reaction mixture was adjusted to 8 with aqueous concentrated
NH4OH solution at 0 ꢀC. The mixture was then extracted with
EtOAc (3 × 20 mL). The combined organic layers were dried
over MgSO4, and the solvent was removed under reduced pres-
sure. The product was purified by flash chromatography with
1
hexane/EtOAc (1:1) giving 90% yield. Yellow oil. H NMR
6. (a) R. L. Rich, A. V. Smirnov, A. W. Schwabacher, J. W. Petrich,
J. Am. Chem. Soc. 1995, 117, 11850.
7. R. S. Obregon, A. Fallis, A. G. Szabo, Can. J. Chem. 1992,
70, 1531.
(400 MHz, CDCl3) δ 8.30 (d, 1H, J = 8.0 Hz), 8.00 (dd, 1H,
J = 8.0 Hz,), 7.35-7.25(m, 3H), 7.05 (d, 1H, J = 8.0 Hz), 6.75
(d, 1H, J = 8.0 Hz), 5.79 (s, 2H), 4.13 (m, 2H), 3.75(m, 1H),
3.34 (m, 1H), 3.13 (m, 1H), 2.30 (brs, 2H), 1.15 (m, 3H),
0.30 (s, 9H); 13C NMR (100 MHz, CDCl3) δ 173.5, 148.9,
142.7, 142.5, 137.5, 136.2, 127.1, 127.0, 125.9, 125.8, 125.4,
125.3, 124.0, 123.9, 119.3, 118.2, 114.0, 59.5, 55.1, 45.8,
30.3, 12.3, 0.11. MS-ESI (m/z) 396.5 (M + 1).
8. L. Lecointe, V. Rolland-Fulcrand, M. L. Roumestant, P. Ville-
font, J. Martinez, Tetrahedron: Asymmetry 1998, 9, 1753.
9. (a) U. Schölkopf, U. Groth, C. Deng, Angew. Chem. Int. Ed.
Engl. 1981, 20, 798; (b) U. Schöllkopf, R. Lonsky, P. Lehr, Lie-
bigsAnn.Chem. 1985, 2, 413;(c)P. Zhang, J. M.Cook, Synthetic
Commun. 1998, 25, 3883.
10. (a) J. Chen, P. Corbin, N. Holman, Org. Process Res. Dev. 2005,
9, 165; (b) A.-C. Carlsson, F. Jam, M. Tullberg, A. Pilotti, P.
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47, 5199.
(R)-7-azatryptophan (8)8
1-Benzyl-2-trimethylsilyl-azatryptophan ethyl ester (181 mg,
0.5 mmol)wasdissolved2 mLof1 Nn-Bu4NCl/THFandstirred
1 h at room temperature. The 2 N aqueous NaOH (1.0 mL)/eth-
anol (1.5 mL) was added to resulting solution, which was heated
to 50 ꢀC for 2 h. The progress of reaction was checked by TLC
with disappeared and new material was on the base. The pH of
resulting mixture was adjusted to 8 with the addition of NH4OH.
Most of the ethanol was removed under reduced pressure. The
desilylated product was debenzylated with 10% Pd/C with 10
mL of ethanol solution under 4 atm for 8 h at room temperature.
After removal of Pd with a silica filter, the solution was cooled
and recrystallized from ethanol/water. 7-Azatryptophan was
obtained with 70% yield (ee = 81%, Chiral HPLC with water/
11. (a) C. Ma, X. Liu, S. Zhao, J. M. Cook, Tetrahedron Lett. 1999,
40, 657; (b) C. Ma, X. He, S. Yu, S. Zhao, J. M. Cook, Tetrahe-
dron Lett. 1999, 40, 2917.
12. (a) R. Liu, P. Zhang, T. Gan, J. M. Cook, J. Org. Chem. 1997, 62,
7447; (b) C. Ma, S. Yu, X. He, X. Liu, J. M. Cook, Tetrahedron
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Tetrahedron Lett. 2004, 45, 8569.
1
ethanol = 70:30). Mp = 261–263 ꢀC. H NMR (D2O) δ 8.70
(dd, 1H, J = 8.0 Hz, J = 1.0 Hz), 8.50 (dd, 1H, J = 6.0 Hz,1.0
Hz), 7.57 (s,1H), 7.66 (dd, 1H J = 7.6 Hz, 6.2 Hz), 4.30 (t, 1H,
J = 6.2 Hz), 3.60 (d, 2H, J = 6.2 Hz). MS-ESI (m/z) 205.2 (M+).
13. (a) R. C. Larock, E. K. Yum, J. Am. Chem. Soc. 1991, 113, 6689;
(b) R. C. Larock, E. K. Yum, M. D. Refvik, J. Org. Chem. 1998,
63, 7652; (c) S. S. Park, J. K. Choi, E. K. Yum, D. C. Ha, Tetra-
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Acknowledgment. Thisworkwasfinanciallysupportedbythe
research fund of Chungnam National University (2014-0679).
14. (a)S. M. Chi, J. K. Choi, E. K. Yum, D. Y. Chi, TetrahedronLett.
2000, 41, 919; (b) K. B. Hong, C. W. Lee, E. K. Yum, Tetrahe-
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