Cross metathesis route in sphingomyelin synthesis

Article abstract of DOI:10.1246/cl.2004.1592

Cross metathesis reaction of short chain Boc sphingosine using Grubbs' 2nd generation catalyst proceeded in stereoselective manner to afford Boc sphingosine in good yield. An efficient synthesis of sphingomyelin was achieved from the obtained Boc sphingos

Full text of DOI:10.1246/cl.2004.1592

1592
Chemistry Letters Vol.33, No.12 (2004)
Cross Metathesis Route in Sphingomyelin Synthesis
Hiroko Hasegawa, Tetsuya Yamamoto, Sho Hatano, Toshikazu Hakogi, and Shigeo Katsumuraꢀ
School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo, 669-1337
(Received September 6, 2004; CL-041048)
Cross metathesis reaction of short chain Boc sphingosine us-
We have also independently investigated this method for the
synthesis of the sphingolipid derivatives. In this paper, we dis-
close our own results of the olefin metathesis for the synthesis
of sphingomyelin as a representative example of sphingolipids.
The substrates were synthesized from oxazolidinone methyl
ester 3 as a chiral building block.8 The monoalkynylation of the
ester 3 with the tert-butyldimethylsilyl ether of propalgyl alcohol
under ꢁ100 ꢂC followed by stereoselective reduction of the re-
sulting ketone 4 with diisobutylaluminum 2,6-di-tert-butyl-4-
methylphenoxide9 provided the corresponding alcohol 5 in
75% yield. The subsequent Birch reduction gave disubstituted
olefin 6 in good yield. Other related compounds 8–13, which
were derived from compound 6 by protecting group manipula-
tion, were used as the substrates of the cross metathesis reaction.
Another segment, 1-pentadecene 7, was synthesized by the
Swern oxidation of commercially available 1-tetradecanol fol-
lowed by the Wittig olefination.
ing Grubbs’ 2nd generation catalyst proceeded in stereoselective
manner to afford Boc sphingosine in good yield. An efficient
synthesis of sphingomyelin was achieved from the obtained
Boc sphingosine using our own phosphorylation reagent.
Sphingolipids are well known as an important class of sec-
ond metabolites found in almost every cell membrane and cyto-
plasm. They are regarded as the lipid secondary messenger in a
cell, and are now accepted to play an important role in signal
transduction and in molecular recognition processes in the cell
membrane.1 Representative sphingolipids include sphingomye-
lin, ceramide, sphingosine, and sphingosine 1-phosphate.
Among them, sphingomyelin has been paid particular attention
because of its important role in maintaining the microdomain
structure in cell membranes which is the so-called raft.2
O
O
sphingomyelinase
ceramidase
Bn
Ph
MeO
N
O
N
O
i
ii
TBSO
O
O
4
3
O
P O
O
C H
15 31
C
13 27
H
NH
NH
NH
2
15 31
O
O
C
H
O
C
H
OH
C H
13 27
OH
13 27
NMe
O
3
OH
OH
OH
sphingosine
O
O
sphingomyelin
ceramide
Bn
HO P O
O
HN
OH
O
N
O
iii
NMe3
TBSO
apoptosis
cell differentiation
inhibition of PKC
5
6
OH
Figure 1. Sphingolipids metabolism.
During the course of our study on sphingolipid synthesis, we
Scheme 1. Reagents and conditions: i) TBSOCH2CCH, n-
BuLi, THF, ꢁ100 ꢂC, 82%, ii) Diisobutylaluminum 2,6-di-tert-
butyl-4-methylphenoxide, toluene, 0 ꢂC, 92%, iii) Li, NH3,
THF, ꢁ78 ꢂC, 90%.
Substrate 8 was used to investigate the reaction conditions
and 10 equivalents of olefin 7 were generally used. Although
the desired cross metathesis reaction did not proceed using the
first generation catalyst 1,10 the 2nd generation catalyst 211 effec-
tively catalyzed the reaction to produce the desired compounds.
After several trials, we found that the reaction was completed by
the addition of 5 mol % catalyst over 6 times. As a result, the sub-
strate 8 stereoselectively provided the desired coupling com-
pound of the E form as the sole product in 69% yield after flash
column chromatography.
The reactions with other substrates were examined and these
results are summarized in Table 1. For the N-Boc compound 9
(Entry 2), almost the same result was obtained. On the other
hand, the reaction of O-Boc compound 10 (Entry 3) showed
no stereoselectivity in 76% yield. For the O-protected opened
chain compounds 11 and 12 (Entries 4 and 5), the coupling prod-
ucts were obtained in low yield or with no stereoselectivity. For-
tunately, the desired N-Boc sphingosine possessing an E olefin
was obtained from alcohol 13 in 62% yield as the sole product
by the use of an 8 mol % catalyst (Entry 6). The use of a smaller
amount of the olefin 7 resulted in a low yield of the desired prod-
have already achieved the syntheses of not only various sphingo-
lipids, such as natural sphingomyelin, ceramide, sphingosine,
sphingosine 1-phosphate, and their short chain analogues,3 but
also fluorescence4 and photo affinity labeled sphingolipids.5
These labeled sphingolipids have been accepted as important
tool molecules for the elucidation of the sphingolipid recognition
processes. However, further convenient and divergent methods
for the synthesis of these various kinds of sphingolipids deriva-
tives including the derivatives in which fluorescence and photo-
affinity groups are introduced into the sphingosine backbone
skeleton, have been desired.
From this aspect, the cross metathesis reaction using a ruthe-
nium catalyst6 is very attractive for providing these various kinds
of sphingolipids from a common intermediate. Quite recently,
two groups independently reported the syntheses of sphingosine
and ceramide by utilizing the olefin cross metathesis method.7
PCy3
Ph
N
N
Mes
Ph
Mes
Cl
Cl
Ru
Cl
Cl
Ru
PCy3
PCy3
1
2
Figure 2. Grubbs’ catalysts.
Copyright Ó 2004 The Chemical Society of Japan

Chemistry Letters Vol.33, No.12 (2004)
1593
Table 1. Cross metathesis reactions using Ru cat. 2a
89% yield. It is noteworthy that the phosphorylation selectively
proceeded at the primary hydroxy group without protection of
the secondary hydroxy group. The obtained bromide showed a
normal polarity and was easily purified by column chromatogra-
phy. Removal of the tert-butoxycarbonyl group of 15 by treat-
ment with trifluoroacetic acid followed by the introduction of
an acyl group onto the resulting primary amine produced amide
16. Finally, the obtained bromide 16 was treated with trimethyl-
amine in methanol in an autoclave at 60 ꢂC to afford natural
sphingomyelin 17 in 46% yield. This is a new route for the syn-
thesis of sphingomyelin.
In conclusion, the cross metathesis method is a very conven-
ient way to produce sphingolipid derivatives and the further de-
velopment of this method for the synthesis of other sphingolipid
derivatives such as fluorescence and photoaffinity labeled com-
pounds is now in progress.
R1
R1
NH
NH
Grubbs cat. 2
OR3
C13H27
OR3
+
C13H27
7
OR2
OR2
Entry
1
Substrate
O
Yield/%
Selectivity
Catalyst/equiv.
0.05 X 6
HN
O
E only
69
67
8
OTBS
O
Boc
N
O
E only
0.05 X 6
2
9
OTBS
O
HN
O
0.05 X 6
0.05 X 6
3
4
76
18
E : Z=18 : 1
10
OBoc
This work was partly supported by a Grant-in-Aid for
Scientific Research from Ministry of Education, Culture, Sports,
Science and Technology, Japan.
Boc
NH
N. D.
OH
11
OTBS
Boc
References and Notes
NH
0.05 X 6
5
mixture of E&Z
N. D.
1
For recent reviews on signal transduction mediated by
sphingolipids, see: a) W. L. Smith and A. H. Merrill, Jr., J.
Biol. Chem., 277, 25841 (2002). b) A. E. Cremesti, F. M. Goni,
and R. Kolesnick, FEBS Lett., 531, 47 (2002) and references
cited therein.
OTBS
OH
12
OTBS
Boc
E only
E only
0.05 + 0.03
0.05 + 0.03
6
7
62
NH
30b
13
2
a) A. Suzuki and Y. Igarashi, Tanpakushitsu Kakusan Koso,
47, 315 (2002). b) K. Simons and E. Ikonen, Science, 290,
1721 (2000). c) K. Simons and E. Ikonen, Nature, 387, 569
(1997) and references cited therein.
OH
aAll reactions were conducted in benzene at 55 ꢂC.
b2 equivalents of 7 were used.
3
4
5
6
M. Murakami, S. Iwama, S. Fujii, K. Ikeda, and S. Katsumura,
Bioorg. Med. Chem. Lett., 7, 1725 (1997).
T. Hakogi, T. Shigenari, S. Katsumura, T. Sano, T. Kohno, and
Y. Igarashi, Bioorg. Med. Chem. Lett., 13, 661 (2003).
T. Shigenari, T. Hakogi, and S. Katsumura, Chem. Lett., 33,
594 (2004).
a) R. H. Grubbs, ‘‘Handbook of Metathesis,’’ Wiley-VCH,
Germany (2003). b) S. J. Connon and S. Blechert, Angew.
Chem., Int. Ed., 42, 1900 (2003) and references cited therein.
a) A. N. Rai and A. Basu, Org. Lett., 6, 2861 (2004). b) S.
Torssell and P. Somfai, Org. Biomol. Chem., 2, 1643 (2004).
a) S. Katsumura, N. Yamamoto, M. Morita, and Q. Han, Tetra-
hedron: Asymmetry, 5, 161 (1994). b) K. Asano, T. Hakogi, S.
Iwama, and S. Katsumura, Chem. Commun., 1999, 41.
S. Iguchi, H. Nakai, M. Hayashi, and H. Yamamoto, J. Org.
Chem., 44, 1363 (1979).
Boc
Boc
NH
NH
i
OH
C13H27
OH
13
OH
14
OH
MeO
MeO
P
O
Br
Boc
A
NH
ii
C13H27
O
O
P
Br
O
OMe
15
OH
7
8
O
C
13H27
NH
iii
C13H27
O
O
P
Br
O
OMe
9
16
OH
O
10 M. S. Sanford, M. Ulman, and R. H. Grubbs, J. Am. Chem.
Soc., 123, 749 (2001).
11 a) M. Scholl, S. Ding, C. W. Lee, and R. H. Grubbs, Org. Lett.,
1, 953 (1999). b) C. Morrill and R. H. Grubbs, J. Org. Chem.,
68, 6031 (2003).
C13H27
C13H27
NH
iv
O
O
P
NMe3
O O
17
OH
Scheme 2. Reagents and conditions: i) see Table 1. ii) CBr4, A,
pyr., 0 ꢂC, 89%. iii) a) TFA, CH2Cl2, 0 ꢂC. b) C13H27COCl,
K2CO3, THF, H2O, 85% for 2 steps. iv) NMe3, MeOH, 46%.
12 Data for A; IR (NaCl neat) 2948, 2838, 1456, 1287, 1181,
1
1005 cmꢁ1; H NMR (CDCl3, 400 MHz) ꢀ 4.10 (td, J ¼ 6:6,
7.6 Hz, 2H), 3.55 (d, J ¼ 10:7 Hz, 6H), 3.49 (t, J ¼ 6:6 Hz,
2H); 13C NMR (CDCl3, 100 MHz) ꢀ 62.0 (JC-P ¼ 11:6 Hz),
49.3 (JC-P ¼ 10:8 Hz), 31.2 (JC-P ¼ 4:1 Hz); 31P NMR (CDCl3,
122 MHz) ꢀ 141.2.
uct (Entry 7).
Furthermore, natural sphingomyelin was conveniently syn-
thesized from the obtained N-Boc sphingosine 14. Phosphoryla-
tion of the compound 14 was successfully realized by a treatment
with compound A,12,13 which was developed in our laboratory,
and carbon tetrabromide in pyridine to give compound 15 in
13 In this time, we have first realized the isolation and
characterization of the compound A. The in situ preparation
of the compound A was reported. E. K. Hendrickson and
H. S. Hendrickson, Chem. Phys. Lipids, 109, 203 (2001).
Published on the web (Advance View) November 13, 2004; DOI 10.1246/cl.2004.1592