Synthesis of all isomers of pulcherrimine, a bitter principle in the sea urchin ovary

Article abstract of DOI:10.1016/S0040-4039(01)02095-0

All eight isomers of pulcherrimine, a bitter principle of the sea urchin (Hemicentrotus pulcherrimus) ovary have been synthesized, which led to revision of the absolute stereochemistry of pulcherrimine. The synthetic pulcherrimine and the 2S isomer were highly bitter at a concentration of 1.0 mM.

Full text of DOI:10.1016/S0040-4039(01)02095-0

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 43 (2002) 115–118
Synthesis of all isomers of pulcherrimine, a bitter principle in the
sea urchin ovary
,†
Noriko U. Sata,* Ryuji Kuwahara and Yuko Murata
Marine Biochemistry Division, National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4, Fukuura,
Kanazawa-ku, Yokohama 236-8648, Japan
Received 3 September 2001; accepted 2 November 2001
Abstract—All eight isomers of pulcherrimine, a bitter principle of the sea urchin (Hemicentrotus pulcherrimus) ovary have been
synthesized, which led to revision of the absolute stereochemistry of pulcherrimine. The synthetic pulcherrimine and the 2S isomer
were highly bitter at a concentration of 1.0 mM. © 2001 Published by Elsevier Science Ltd.
Recently, we reported the isolation and structure deter-
mination of pulcherrimine, a bitter principle of the sea
urchin (Hemicentrotus pulcherrimus) ovary. The struc-
Synthesis of pulcherrimine isomers. The retrosynthetic
study readily resulted in the strategy outlined in Scheme
1. Michael addition of fully protected 4-thioacetyl-2-
piperidinecarboxylic acid (3) to benzoyl enolate 2, fol-
lowed by deprotection will lead to all isomers of
pulcherrimine. 4-Thioacetyl-2-piperidinecarboxylic acid
methyl ester (3) can be derived from 4-bromo-1-butene
1
ture of pulcherrimine was determined to be a novel
sulfur-containing amino acid, 4S-(2%-carboxy-2%R-
hydroxy-ethylthio)-2R-piperidinecarboxylic acid (1).
Since pulcherrimine has three chiral centers, it is interest-
ing to clarify the effect of their stereochemistry on the
bitter taste of pulcherrimine. In this paper we describe
the synthesis and bitterness of all eight stereoisomers of
pulcherrimine.
(
4) and (R)-(+)-a-methylbenzylamine (5).
Among a number of methods to prepare 4-hydroxy-2-
2–4
5
6
piperidinecarboxylic acid, those of Skiles and Gillard
OH
were adopted here. Starting from the commer-
cially available (R)-(+)-a-methyl benzylamine (5) and
S 4
2 COOH
NH
HOOC 2'
4
-bromo-1-butene (4), N-Boc-4-hydroxy-2-piperidine-
carboxylic acid methyl ester (6a) was prepared essen-
tially according to the literature,
5–7
Pulcherrimine (1)
whereas 6b was
OBz
MeOOC
2
OH
S
COOH
NH
HOOC
+
SAc
1
NH2
Me
+
Br
4
N
Boc
COOMe
3
5
Scheme 1.
*
Corresponding author. Present address: Department of Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi,
Kohoku-ku, Yokohama 223-8522, Japan. Tel.: +81-45-566-1706; fax: +81-45-566-1697; e-mail: nonno@chem.keio.ac.jp
Domestic Research Fellow.
†
0
040-4039/02/$ - see front matter © 2001 Published by Elsevier Science Ltd.
PII: S0040-4039(01)02095-0

1
16
N. U. Sata et al. / Tetrahedron Letters 43 (2002) 115–118
1
1–13
prepared from (2S,4R)-lactone (Scheme 2). Overall
yields of two esters, 6a and 6b were 99 and 97% from
the corresponding lactones, respectively.
from
L
- and
D
-serine in three steps (Scheme 4).
The
1
H NMR spectrum of the synthetic (2%S,2R,4S)-isomer
1a was identical with that of the natural pulcherrimine.
This result was contradictory to that obtained previ-
ously. Moreover, chiral HPLC analysis using a
SUMICHIRAL OA-5000 column led the same result.
Finally, modified Mosher analysis applied to the N-
Boc methyl ester derived from the natural pulcherrim-
ine disclosed the 2%S-stereochemistry (Fig. 1). Thus, the
stereochemistry of pulcherrimine was revised to 2%S, 2R
and 4S.
1
Compound 6a was treated with MsCl to obtain the
mesylate 7a in 98% yield, which was reacted with
1
4
15
potassium thioacetate to afford the (2R,4R)-thioacetate
8
3
b in 42% yield as shown in Scheme 2. On the other
hand, the mesylate 7a was converted to the iodide
which was treated with potassium thioacetate to give
another diastereomer (2R,4S)-thioacetate 3a in 49%
yield. In the same manner, 3c and 3d were derived from
6b.
Bitterness of pulcherrimine isomers. A panel of three
people evaluated bitterness of aqueous solutions of the
natural pulcherrimine and synthetic eight isomers. Syn-
thetic (2%S,2R,4S)-isomer 1a, (2%S,2S,4S)-isomer 1g and
(2%R,2S,4S)-isomer 1h were bitter, among which 1a was
most bitter, as bitter as the natural pulcherrimine.
(2%S,2S,4S)-Isomer 1g was also highly bitter, but tasted
different from pulcherrimine. The detection and recog-
nition thresholds for 1g and 1h were estimated to be
Michael addition of N-Boc-4-thioacetyl-piperidinecar9-
boxylic acid methyl ester (3a) to the benzoyl enolate 2
was effected with NaOMe in the presence of NaBH4,
which was accompanied by deprotection of acetate and
benzoate to afford two diastereomers at the 2%-position
[
(2%S,2R,4S)-isomer 8a and (2%R,2R,4S)-isomer 8b] as
shown in Scheme 3. These diastereomers were separated
1
6,17
by repeated MPLC on silica gel with hexane/Et O (1:4),
0.192/0.306 mM and 0.250/0.500 mM, respectively.
2
hexane/Et O/EtOH (20:80:0.1), or on ODS with
2
MeCN/H O (30:70) to obtain pure 8a and 8b in 38 and
2
3
1
4% yields, respectively, which were deprotected with
Acknowledgements
M HCl at 100°C to give quantitative 1a and 1b,
respectively. The other 6 isomers 1c–1h were synthe-
sized in the same fashion.
We are grateful to Professor Nobuhiro Fusetani, Uni-
versity of Tokyo, for his critical reading of the
manuscript. A Domestic Research Fellowship of Japan
Science and Technology Corporation to N.U.S. is
acknowledged.
To determine the stereochemistry at C2%-position in all
1
0
isomers obtained, 1a–1h were synthesized from chiral
benzyl glycidates, instead of 2, which were prepared
SAc
OH
OMs
N
N
Boc
COOMe
f, g
g
3a (2R,4S)
e
N
COOMe
COOMe
SAc
Boc
Boc
6a
7a
N
COOMe
NH2
Me
Boc
3b (2R,4R)
a-d
+
Br
4
SAc
5
OH
OMs
N
Boc
3c (2S,4R)
COOMe
f, g
g
e
N
Boc
COOMe
N
Boc
7b
COOMe
SAc
6b
N
COOMe
Boc
3d (2S,4S)
Scheme 2. Reagents and conditions: (a) Et N, MeCN; (b) i. OHCCOOH, 4 A MS, MeCN, ii. separation of diastereomers; (c)
,
3
H /Pd(OH) , HCl–MeOH; (d) Boc O, Et N; (e) MsCl, CH Cl , pyr., DMAP; (f) NaI, acetone, reflux; (g) MeCOSK, MeCN,
2
2
2
3
2
2
reflux.

N. U. Sata et al. / Tetrahedron Letters 43 (2002) 115–118
117
OH
MeOOC 2'
OH
OBz
a
S
4
2
COOMe
S
COOMe
NBoc
+
3a
+ MeOOC
MeOOC
2
NBoc
b, c
8a
8b
b, c
1a (2'S,2R,4S)
1b (2'R,2R,4S)
OH
OH
S
OBz
OBz
a
a
S
COOMe
COOMe
+
+
3b
3c
+ MeOOC
MeOOC
MeOOC
MeOOC
2
NBoc
NBoc
8c
8d
b, c
b, c
1c (2'S,2R,4R)
1d (2'R,2R,4R)
OH
OH
S
S
COOMe
COOMe
+ MeOOC
MeOOC
2
NBoc
NBoc
8
e
8f
b, c
b, c
1
e (2'S,2S,4R)
1f (2'R,2S,4R)
OH
OH
S
OBz
a
S
COOMe
COOMe
+
3d
+
MeOOC
MeOOC
MeOOC
2
NBoc
b, c
NBoc
b, c
8
g
8h
1
g (2'S,2S,4S)
1h (2'R,2S,4S)
Scheme 3. Reagents and conditions: (a) NaBH (0.5 equiv.), NaOMe (2.5 equiv.), MeOH, 0°C; (b) 1 M aq. HCl, 100°C; (c) HPLC
4
purification.
OH
nic, D.; Yoakim, C. J. Org. Chem. 1997, 62, 3440–3448.
O
a
S
4
2
COOMe
NBoc
b, c
+
3a
4. Nardo, C. D.; Varela, O. J. Org. Chem. 1999, 64, 6119–
125 and references cited therein.
MeOOC 2'
BnOOC
benzyl glycidate
6
5
. Skiles, J. W.; Giannousis, P. P.; Fales, K. R. Bioorg.
Med. Chem. Lett. 1996, 6, 963–966.
. Gillard, J.; Abraham, A.; Anderson, P. C.; Beaulieu, P.
L.; Bogri, T.; Bousquet, Y.; Grenier, L.; Guse, I.;
Lavallee J. Org. Chem. 1996, 61, 2226–2231.
8a
1a (2'S,2R,4S)
6
Scheme 4. Reagents and conditions: (a) NaBH (0.5 equiv.),
4
NaOMe (2.5 equiv.), MeOH, 0°C; (b) 1 M aq. HCl, 100°C;
7. Mccague, R. Modern Drug Discovery 2000, 3, 29, 31–32,
(
c) HPLC purification.
34.
8
. Miyauchi, M.; Endo, R.; Hisaoka, M.; Yasuda, H.;
Kawamoto, I. J. Antibiot. 1997, 50, 429–439.
+
+
0.100
0.075
OMTPA
+0.039
COOMe
+
0.281
+
0.021
S
4
2
9. Ikota, N.; Takamura, N.; Young, S. D.; Ganem, B.
MeOOC 2'
+0.205
-0.042
+0.128
0.025
Tetrahedron Lett. 1981, 22, 4163–4166.
+
NBoc
22
D
+
0.241
+0.008
10. Spectral data of eight isomers: 1a (2%S,2R,4S) [h] −13.3°
+
0.234 +0.123
24
(
c 0.10, H O) [lit. natural [h]D −16.5° (c 0.20, H O)];
2 2
+
HRFABMS m/z 250.0736 (M+H) C H O NS (D +1.6
mmu). 1f (2%R,2S,4R). [h]D +12.4° (c 0.20, H O);
HRFABMS m/z 250.0739 (M+H) C H O NS (D −1.1
mmu). Other spectral data are identical with those of
9
16
5
22
2
Figure 1. Dl values obtained for MTPA esters of pulcherrim-
+
9
16
5
ine derivative.
23
natural pulcherrimine. 1b (2%R,2R,4S). [h]D −18.8° (c
References
0
.20, H O); IR (film) w
3423, 3080, 2970, 1727, 1631,
2
max
−
1 1
1400, 1286, 1102 cm ; H NMR in D O–CD OD (40:1)
2
3
1
2
3
. Murata, Y.; Sata, N. U. J. Agric. Food. Chem. 2000, 48,
557–5560.
. Hays, S. J.; Malone, T. C.; Johnson, G. J. Org. Chem.
991, 56, 4084–4086 and references cited therein.
. Beaulieu, P. L.; Lavallee, P.; Abraham, A.; Anderson, P.
C.; Boucher, C.; Bousquet, Y.; Ducepeppe, J.-S.; Gillard,
J.; Gorys, V.; Grand-Maitre, C.; Grenier, L.; Guindon,
Y.; Guse, I.; Plamondon, L.; Soucy, F.; Valois, S.; Wer-
l 4.19 (1H, dd, J=6.8, 3.9 Hz), 3.64 (1H, dd, J=12.7, 3.4
Hz), 3.49 (1H, ddd, J=13.2, 4.4, 2.5 Hz), 3.10 (1H, m),
5
3.05 (1H, dd, J=13.7, 3.9 Hz), 3.04 (1H, m), 2.90 (1H,
1
dd, J=13.7, 6.8 Hz), 2.59 (1H, m), 2.24 (1H, m), 1.64
13
(
1H, m), 1.61 (1H, m); C NMR in D O–CD OD (40:1)
2 3
l 180.0 s, 174.3 s, 72.5 d, 60.0 d, 44.1 t, 39.6 d, 35.3 t,
+
34.3 t, 29.8 t; HRFABMS m/z 250.0741 (M+H)
23
C H O NS (D −0.8 mmu). 1e (2%S,2S,4R). [h] +20.8° (c
9
16
5
D

1
18
N. U. Sata et al. / Tetrahedron Letters 43 (2002) 115–118
+
+
23
D
+
0
.20, H O); HRFABMS m/z 250.0736 (M+H)
(M+H) C H O NS (D +1.6 mmu). 1g (2%S,2S,4S). [h]
2
9
16
5
C H O NS (D −1.3 mmu). Other spectral data are identi-
cal with those of 1b. 1c (2%S,2R,4R). [h]D +12.8° (c 0.20,
H O); IR (film) w 3419, 1715, 1633, 1395, 1315, 1090
0° (c 0.25, H O); HRFABMS m/z 250.0728 (M+H)
9
16
5
2
23
C H O NS (D −2.1 mmu). Other spectral data are identi-
9
16
5
2
max
cal with those of 1d.
−
1 1
cm ; H NMR in D O–CD OD (40:1) l 4.09 (1H, dd,
2
3
11. Larcheveque, M.; Petit, Y. Tetrahedron Lett. 1987, 28,
J=6.8, 3.9 Hz), 3.86 (1H, dd, J=10.3, 4.4 Hz), 3.29 (1H,
quint, J=4.4 Hz), 3.22 (1H, m), 3.21 (1H, m), 2.90 (1H,
dd, J=13.7, 3.9 Hz), 2.79 (1H, dd, J=13.7, 6.8 Hz), 2.15
1
993–1996.
2. Roush, W. R.; Brown, B. B. J. Org. Chem. 1992, 57,
380–3387.
1
1
1
3
13
(1H, m), 2.10 (1H, m), 2.03 (1H, m), 1.83 (1H, m);
C
3. Roush, W. R.; Koyama, K.; Curtin, M. L.; Moriarty, K.
J. J. Am. Chem. Soc. 1996, 118, 7502–7512.
4. Eight isomers could be separated by chiral HPLC on
NMR in D O–CD OD (40:1) l 180.0 s, 174.7 s, 72.4 d,
2
3
5
5.6 d, 40.6 t, 38.5 d, 36.1 t, 32.2 t, 27.9 t; HRFABMS
+
m/z 250.0739 (M+H) C H O NS (D −1.9 mmu). 1h
9
16
5
SUMICHIRAL OA-5000 (4.6 150 mm) with MeCN/H O
23
2
(2%R,2S,4S). [h] −13.3° (c 0.20, H O); HRFABMS m/z
D 2
+
(
15:85) containing 2 mM CuSO (detection, UV 254 nm;
4
2
50.0739 (M+H) C H O NS (D +0.3 mmu). Other spec-
9
16
5
flow rate, 1.0 mL/min; column temperature, 50°C).
Retention times: natural pulcherrimine (1, 49.3 min),
synthetic pulcherrimine (1a, 49.9 min), 1b (33.3 min), 1c
tral data are identical with those of 1c. 1d (2%R,2R,4R).
2
3
[
h] 0° (c 0.25, H O); IR (film) w
3412, 3043, 1725,
D
2
max
1
−
1
1
627, 1398, 1282, 1219, 1097 cm ; H NMR in D O–
2
(
(
43.9 min), 1d (27.1 min), 1e (23.2 min), 1f (15.2 min), 1g
27.1 min) and 1h (19.4 min).
CD OD (40:1) l 4.12 (1H, dd, J=6.8, 3.9 Hz), 3.86 (1H,
3
dd, J=9.8, 4.4 Hz), 3.30 (1H, quint, J=4.4 Hz), 3.22
1
5. Ohtani, I.; Kusumi, T.; Kashman, Y.; Kakisawa, H. J.
(1H, m), 3.21 (1H, m), 2.96 (1H, dd, J=13.7, 3.9 Hz),
Am. Chem. Soc. 1991, 113, 4092–4096.
2
.78 (1H, dd, J=13.7, 6.8 Hz), 2.16 (1H, m), 2.12 (1H,
13
16. Patton, S.; Josephason, D. V. Food Res. 1957, 22, 316–
18.
17. Bartoshuk, L. M. Am. J. Clin. Nutr. 1978, 32, 1622–1627.
m), 2.03 (1H, m), 1.84 (1H, m); C NMR in D O–
2
3
CD OD (40:1) l 180.0 s, 174.7 s, 72.3 d, 55.6 d, 40.5 t,
3
3
8.5 d, 36.2 t, 32.4 t, 27.7 t; HRFABMS m/z 250.0765
.