2788
M. Kaname et al. / Tetrahedron Letters 49 (2008) 2786–2788
2
. (a) Sheehan, J. C.; Tulis, R. W. J. Org. Chem. 1974, 39, 2264–2267; (b)
Carlsen, P. H. J.; Katsuki, T.; Martin, V. S.; Sharpless, K. B. J. Org.
Chem. 1981, 46, 3936–3938.
RuO4
COOMe
HOOC
COOMe
N
Boc
HN
Boc
tert-BuOH
2 days, 68%
3
. (a) Yoshifuji, S.; Arakawa, Y.; Nitta, Y. Chem. Pharm. Bull. 1985, 33,
1
5
042–5047; (b) Yoshifuji, S.; Tanaka, K.; Kawai, T.; Nitta, Y. Chem.
11
12
Pharm. Bull. 1985, 33, 5515–5521; (c) Yoshifuji, S.; Tanaka, K.;
Kawai, T.; Nitta, Y. Chem. Pharm. Bull. 1986, 34, 3873–3878.
RuO4
4. (a) Yoshifuji, S.; Tanaka, K.; Nitta, Y. Chem. Pharm. Bull. 1985, 33,
1749–1751; (b) Tanaka, K.; Yoshifuji, S.; Nitta, Y. Chem. Pharm.
Bull. 1987, 35, 364–369; (c) Yoshifuji, S.; Tanaka, K.; Nitta, Y. Chem.
Pharm. Bull. 1987, 35, 2994–3000.
HOOC
HOOC
N
Boc
COOMe
COOMe
HN
Boc
COOMe
tert-BuOH
days, 88%
2
5
4 4
. Double layer system using NaIO aqueous solution and CCl requires
13
14
long reaction time: Nakata, H. Tetrahedron 1963, 19, 1959–1963.
. (a) Yoshifuji, S.; Matsumoto, H.; Tanaka, K.; Nitta, Y. Tetrahedron
Lett. 1980, 21, 2963–2964; (b) Tanaka, K.; Yoshifuji, S.; Nitta, Y.
Chem. Pharm. Bull. 1986, 34, 3879–3884; (c) Kaname, M.; Yoshifuji,
S. Tetrahedron Lett. 1992, 33, 8103–8104; (d) Yoshifuji, S.; Kaname,
M. Chem. Pharm. Bull. 1995, 43, 1302–1306; (e) Yoshifuji, S.;
Kaname, M. Chem. Pharm. Bull. 1995, 43, 1617–1620.
6
RuO4
N
Boc
HN
COOMe
tert-BuOH
days, 84%
3
Boc
15
1
6
7. Ito, R.; Umezawa, N.; Higuchi, T. J. Am. Chem. Soc. 2005, 127, 834–
35.
. Typical procedure for the RuO
amino acid: A solution of N-benzoylpyrrolidine (1a, 6 mmol) to be
oxidized in tert-butanol (20 mL) was added to mixture of
RuO O (60 mg) and 10% NaIO aqueous solution (80 mL).
8
Scheme 4.
8
4
oxidation of N-acylamino acid to x-
a
Next, we planned the deployment of this single layer
2
ꢀxH
2
4
RuO4 oxidation into the optically active compounds.
Four-membered N-Boc cyclic imino acid ester 11 was oxi-
dized under similar conditions to give the corresponding
The aqueous mixture was vigorously stirred in a sealed flask at room
temperature for 5 h. After the starting material had disappeared, ethyl
acetate (100 mL) and water (50 mL) were added to the mixture, the
organic layer was separated. The aqueous layer was extracted with
ethyl acetate (50 mL ꢃ 2), and then isopropanol (3 mL) was added to
the combined organic mixture. The mixture was stirred for further 2 h
19
10
23
D
optically active x-amino acid 12 [½aꢁ ꢂ19.9° (lit. ½aꢁ
D
ꢂ19°)] in 68 yield without any loss of chirality at the C-2
position of the cyclic amine 11. Similarly, the optically
active x-amino acids 14 and 16 were obtained by the oxida-
tion of the corresponding imino acid esters 13 and 15 in
for the decomposition of the RuO
(RuO2) was filtered off. The filtrate was washed with brine
SO , and then evaporated. The resulting
4
oxidant, and the black precipitate
(
50 mL ꢃ 2), dried over Na
2
4
crude acid was purified by column chromatography on silica gel to
8
8% and 84% yields, respectively (Scheme 4).
In summary, simple RuO oxidized cyclic N-acylamines
give 3a (64%, colorless prisms, mp 77–78 °C) and 2a (6%, colorless
4
11
12
prisms, mp 89–90 °C). Compounds 3a and 2a were identical with
to afford x-amino acids under a single layer system using a
NaIO4 solution containing tert-butanol in moderate to
good yields. This oxidative system can successfully be
applied to optically active cyclic imino acid esters produc-
ing x-amino acids having an ester moiety at the a position
of the amino group. A significant reaction mechanism of
this oxidation reaction is proposed.
authentic samples, respectively.
9. Typical procedure for the preparation of N-acyl x-amino acid methyl
ester: N-tert-Butoxycarbonylpyrrolidine (1b, 6 mmol) was oxidized
and worked up as described for the preparation of 3a to give the crude
acid 3b. Excess ethereal diazomethane was added to acid 3b in MeOH
(
1
30 mL). The reaction mixture was stirred at room temperature for
h, and evaporated. The obtained crude ester was purified by short
column chromatography on silica gel to give 4a (79%) as a colorless
oil. IR (KBr): m; 3373 (NH), 1738 (COOMe), 1716 (COOt-Bu); MS:
+
+
m/z: 216 (M ꢂ1); HRMS: calcd for C10
H
18NO
4
(M ꢂ1) 216.1236.
Acknowledgments
1
Found: 216.1239; H NMR (500 MHz, CDCl
3
): d 1.44 (9H, s, t-Bu),
1
.79–1.82 (2H, m, 3-H), 2.36 (2H, t, J = 6.4 Hz, 2-H), 3.16 (2H, q,
The authors are indebted to Ms. Noriko Ando for her
experimental efforts. This work was partially supported
by The Specific Research Fund of Hokuriku University
13
J = 6.5 Hz, 4-H), 3.68 (3H, s, OMe), 4.70–4.82 (1H, br s, NH);
NMR (125 MHz, CDCl ): d 25.3 (t, C3), 28.41 and 79.2 (q and s,
t-Bu), 31.3 (t, C2), 39.9 (t, C4), 51.7 (q, OMe), 156.0 (s, NC@O), 173.8
C
3
(
s, C1).
(
2007).
1
1
0. Cantacuzene, D.; Guerreiro, C. Tetrahedron 1989, 45, 741–748.
1. (a) Todd, D.; Teich, S. J. Am. Chem. Soc. 1953, 75, 1895–1900; (b)
Barluenga, J.; Foubelo, F.; Fananas, F. J.; Yus, M. Tetrahedron 1989,
References and notes
4
5, 2183–2192.
1
. (a) Lee, D. G.; van den Engh, M. In Oxidation in Organic Chemistry;
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