Formal synthesis of (+)-3-Deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN) via desymmetrization by ring-closing metathesis

Article abstract of DOI:10.1021/ol006887l

equation presented Formal synthesis of the naturally occurring deaminated sialic acid KDN, a potential oncofetal antigen, has been accomplished in 45% overall yield via a novel ketalization/ring-closing metathesis sequence. The rapid introduction of all o

Full text of DOI:10.1021/ol006887l

ORGANIC
LETTERS
2001
Vol. 3, No. 2
237-240
Formal Synthesis of (+)-3-Deoxy-D-
glycero-D-galacto-2-nonulosonic Acid
(KDN) via Desymmetrization by
Ring-Closing Metathesis
Steven D. Burke* and Eric A. Voight
Department of Chemistry, UniVersity of Wisconsin-Madison, 1101 UniVersity AVenue,
Madison, Wisconsin 53706-1396
burke@chem.wisc.edu
Received November 17, 2000
ABSTRACT
Formal synthesis of the naturally occurring deaminated sialic acid KDN, a potential oncofetal antigen, has been accomplished in 45% overall
yield via a novel ketalization/ring-closing metathesis sequence. The rapid introduction of all oxygen functionality in a completely stereocontrolled
manner exploited a rigid 6,8-dioxabicyclo[3.2.1]oct-2-ene ring system. This general synthetic strategy should provide access to a number of
KDN and sialic acid analogues.
We recently reported short syntheses of (+)-exo-, rac-endo-,
and enantiomerically enriched (+)-endo-brevicomin employ-
ing catalytic ring-closing olefin metathesis as a novel method
for substrate desymmetrization in constructing the 6,8-
dioxabicyclo[3.2.1]octane ring system.1 To expand the utility
of our intermolecular ketalization/intramolecular C-C bond
formation strategy (Figure 1), the synthesis of more complex
natural products has been pursued. These efforts have
culminated in a short and efficient formal synthesis of (+)-
3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN, 1,
Figure 2), a deaminated sialic acid first isolated by Inoue in
1986 from the membrane polysialoglycoproteins of rainbow
trout eggs.2a While KDN is thought to protect the egg
membrane from attack by bacterial sialidases in the rainbow
trout,2b the more recent discovery of elevated levels of free
KDN in human fetal cord red blood cells and ovarian cancer
cells indicates oncofetal antigen properties that could be
important in the early detection of disease and as a marker
for detecting disease recurrence.2c
(1) Burke, S. D.; Mu¨ller, N.; Beaudry, C. M. Org. Lett. 1999, 1, 1827-
1829.
(2) (a) Nadano, D.; Iwasaki, M.; Endo, S.; Kitajima, K.; Inoue, S.; Inoue,
Y. J. Biol. Chem. 1986, 261, 11550-11557. (b) Schreiner, E.; Zbiral, E.
Liebigs Ann. Chem. 1990, 581-586. (c) Inoue, S.; Lin, S.-L.; Chang, T.;
Wu, S.-H.; Yao, C.-W.; Chu, T.-Y.; Troy, F. A., II; Inoue, Y. J. Biol. Chem.
1998, 273, 27199-27204.
Figure 1. General strategy.
10.1021/ol006887l CCC: $20.00 © 2001 American Chemical Society
Published on Web 12/29/2000

functionalization and ultimate hydrolysis of the bicyclic
acetal template. The electron rich 3,4-dimethoxy-benzene
carboxyl surrogate5 was chosen to facilitate acetal hydrolysis
prior to oxidative unmasking of the acid, avoiding potential
difficulties in the ring opening.3a Tetraol 3 appeared readily
accessible from diene 4 via a double Sharpless asymmetric
dihydroxylation6,7 using the recently developed (DHQ)2AQN
ligand6b to properly set the C-8 stereocenter. To access
tetraacetate 2 from 3 would require an inversion to secure
the natural C-4 configuration of KDN. The diene 4 was en-
visioned as the product of a ring-closing metathesis reaction
of pseudo-C2-symmetric triene 5, which could be obtained
via an intermolecular ketalization/elimination sequence1
between enantiomerically pure diene diol 67 and ketone 7.8
The formal synthesis of KDN began with an acid cat-
alyzed ketalization between 6 and 7, both of which were
readily prepared on a large scale by modified literature
procedures (Scheme 1).7,8 Careful optimization was needed
Figure 2. Retrosynthetic analysis.
Scheme 1. Synthesis of Tetraol 3
Since its isolation, KDN has been the subject of consider-
able synthetic interest.2b,3 Total syntheses by Dondoni,3a
Takahashi,3b and Banwell3c have appeared, but most work
in this area has focused on the enzymatic3d-i or chemical3j-q
elongation of D-mannose or its derivatives. Each previous
total synthesis has involved extensive protection/deprotection
and/or nonselective reactions. Each mannose elongation
strategy has utilized four starting material stereocenters and
native functionality, which, while expeditious for KDN,
limits possibilities for derivative synthesis. Many derivatives
of KDN,2b,3a,j,4 such as C-glycosides,4a-c amino derivatives,4d-j
deoxy sugars,2b,4k,l unsaturated analogues,4f,j,m-p and epimers,3a,j
have been identified and pursued as important synthetic
building blocks, biological probes, and drug candidates, sug-
gesting the need for an efficient and versatile synthesis route.
Our retrosynthetic analysis of KDN revealed the protected
2,7-anhydro sugar derivative 2 as a suitable precursor (Figure
2). The hydropyran ring in bicyclic acetal 2 is constrained
to be in the opposite chair conformation from that in KDN,
forcing four of five substituent groups into axial orientations.
This feature was expected to assist both stereoselective
due to inhibition of the reaction by the electron rich aromatic
ring and the known instability of γ-haloketones.9 Refluxing
a benzene solution of diene diol 6 (1 equiv, 0.5 M), CSA
(0.1 equiv), and ketone 7 (2 equiv) with azeotropic removal
of water gave ketal 8 (90%) on a 10 g scale. Selenide
displacement, oxidation, and eliminination following Sharp-
less’ procedure10 produced triene 5 in 96% yield. All attempts
to prepare 5 by ketalization between diene diol 6 and the
appropriate â,γ-unsaturated ketone gave only the product
resulting from double bond migration.
With triene substrate 5 in hand, ring-closing metathesis
proceeded readily using the Grubbs ruthenium benzylidene
catalyst 9 (0.02 equiv, Scheme 1).11 This reaction was best
performed by adding the catalyst in benzene slowly over 1.5
h to a refluxing solution of 5 in benzene (0.01 M), giving
5-aryl-7-vinyl-6,8-dioxabicyclo-[3.2.1]oct-2-ene 4 (91%). A
double dihydroxylation using the conditions previously
(3) (a) Dondoni, A.; Marra, A.; Merino, P. J. Am. Chem. Soc. 1994,
116, 3324-3336. (b) Tsukamoto, H.; Takahashi, T. Tetrahedron Lett. 1997,
38, 6415-6418. (c) Banwell, M.; De Savi, C.; Watson, K. J. Chem. Soc.,
Chem. Commun. 1998, 1189-1190. (d) Auge´, C.; Gautheron, C. J. Chem.
Soc., Chem. Commun. 1987, 859-860. (e) Auge´, C.; Bouxom, B.; Cavaye´,
B.; Gautheron, C. Tetrahedron Lett. 1989, 30, 2217-2220. (f) Auge´, C.;
Gautheron, C.; David, S.; Malleron, A.; Cavaye´, B.; Bouxom, B. Tetrahe-
dron 1990, 46, 201-214. (g) Lin, C.-H.; Sugai, T.; Halcomb, R. L.;
Ichikawa, Y.; Wong, C.-H. J. Am. Chem. Soc. 1992, 114, 10138-10145.
(h) Sugai, T.; Kuboki, A.; Hiramatsu, S.; Okazaki, H.; Ohta, H. Bull. Chem.
Soc. Jpn. 1995, 68, 3581-3589. (i) Salagnad, C.; Go¨dde, A.; Ernst, B.;
Kragl, U. Biotechnol. Prog. 1997, 13, 810-813. (j) Shirai, R.; Ogura, H.
Tetrahedron Lett. 1989, 30, 2263-2264. (k) Turik, S. V.; Bicherova, I. I.;
Kornilov, V. I.; Zhdanov, Y. A. Dokl. Akad. Nauk SSSR 1991, 318, 152-
154. (l) Chan, T.-H.; Li, C.-J. J. Chem. Soc., Chem. Commun. 1992, 747-
748. (m) Sato, K.-i.; Miyata, T.; Tanai, I.; Yonezawa, Y. Chem. Lett. 1994,
129-132. (n) Chan, T.-H.; Li, C. J.; Lee, M.-C.; Wei, Z. Y. Can. J. Chem.
1994, 72, 1181-1192. (o) Chan, T.-H.; Lee, M.-C. J. Org. Chem. 1995,
60, 4228-4232. (p) Chan, T.-H.; Isaac, M. B. Pure Appl. Chem. 1996, 68,
919-924. (q) Warwel, M.; Fessner, W. D. Synlett 2000, 6, 865-867. (r)
Shirai, R.; Nakamura, M.; Hara, S.; Takayanagi, H.; Ogura, H. Tetrahedron
Lett. 1988, 29, 4449-4452.
238
Org. Lett., Vol. 3, No. 2, 2001

reported7 provided tetraol 3 (94%) as white pellets after
chromatography to remove iron salt impurities and recrys-
tallization from EtOAc to remove coeluting anthraquinone
ligand. No other stereoisomers were detected in the 1H NMR
of 3 before or after recrystallization. Use of the (DHQ)2AQN
ligand,6b which has been shown to increase the rate and
stereoselectivity of reactions with terminal alkenes, was
needed for dihydroxylation of the terminal olefin to occur.
When commercially available AD-mix-R was used, only the
internal olefin experienced dihydroxylation.
Scheme 2. Completion of the Total Synthesis
While the rigid bicyclic framework of 3 clearly set the
stereochemistry of the C-4, C-5 vicinal diol on the six-
membered ring as evidenced by 1H NMR coupling constants
(H-3ax:H-4 ) 11 Hz; H-3eq:H-4 ) 6.5 Hz; H-4:H-5 ) 4 Hz),
the C-8 stereochemistry could not be determined by NMR.
To confirm that this stereocenter had been correctly set, 3
was converted to dithionocarbonate derivative 10 (Figure 3).
was peracetylated to give ditosylate diacetate 11. The use
of stoichiometric amounts of tin for stannylene acetal
formation to achieve selective equatorial protection of a
sugar-derived cis vicinal diol is well-known,14 but this is the
first example using a catalytic amount of tin.15
Because of its limited stability, 11 was routinely taken on
to the next reaction by addition of toluene to the combined
pure fractions of 11 after column chromatography. Following
evaporation of the chromatography solvent (ether), cesium
acetate (10 equiv) and 18-crown-6 (2 equiv) were added.
Heating at reflux for 18 h gave inverted tetraacetate 216 (81%
overall from 3 after one recycling of recovered monotosylate
triacetate). This sluggish SN2 reaction failed when other
solvents or oxygen nucleophiles were utilized.
(4) (a) Nakamura, M.; Takeda, K.; Takayanagi, H.; Asai, N.; Ibata, N.;
Ogura, H. Chem. Pharm. Bull. 1993, 41, 26-30. (b) Du, Y.; Polat, T.;
Linhardt, R. J. Tetrahedron Lett. 1998, 39, 5007-5010. (c) Polat, T.; Du,
Y.; Linhardt, R. J. Synlett 1998, 1195-1196. (d) Nakamura, M.; Furuhata,
K.; Yamasaki, T.; Ogura, H. Chem. Pharm. Bull. 1991, 39, 3140-3144.
(e) Sun, X.-L.; Haga, N.; Ogura, H.; Takayanagi, H. Chem. Pharm. Bull.
1994, 42, 2352-2356. (f) Sun, X.-L.; Kai, T.; Tanaka, M.; Takayanagi,
H.; Furuhata, K. Chem. Pharm. Bull. 1995, 43, 1654-1658. (g) Kok, G.
B.; Itzstein, M. v. Synthesis 1997, 769-772. (h) Kai, T.; Sun, X.-L.;
Takayanagi, H.; Furuhata, K. J. Carbohydr. Chem. 1997, 16, 533-540. (i)
Sun, X.-L.; Kai, T.; Takayanagi, H.; Furuhata, K. Carbohydr. Res. 1997,
298, 181-189. (j) Sun, X.-L.; Sato, N.; Kai, T.; Furuhata, K. Carbohydr.
Res. 2000, 323, 1-6. (k) Lubineau, A.; Argostanzo, H.; Queneau, Y. J.
Carbohydr. Chem. 1995, 14, 1307-1328. (l) Shen, X.; Wu, Y.-L.; Wu, Y.
HelV. Chim. Acta 2000, 83, 943-953. (m) Sun, X.-L.; Kai, T.; Takayanagi,
H.; Furuhata, K. J. Carbohydr. Chem. 1997, 16, 541-547. (n) Kok, G. B.;
Norton, A. K.; Itzstein, M. v. Synthesis 1997, 1185-1188. (o) Sun, X.-L.;
Kai, T.; Sato, N.; Takayanagi, H.; Furuhata, K. J. Carbohydr. Chem. 1999,
18, 1131-1138. (p) Nakamura, M.; Furuhata, K.; Ogura, H. Chem. Pharm.
Bull. 1988, 36, 4807-4813. (q) Nakamura, M.; Furuhata, K.; Ogura, H.
Chem. Pharm. Bull. 1989, 37, 821-823.(r) Herunsalee, A.; Isobe, M.; Pikul,
S.; Goto, T. Synlett 1991, 199-201. (s) David, S.; Malleron, A.; Cavaye´,
B. Carbohydr. Res. 1994, 260, 233-241. (t) Kok, G. B.; Mackey, B. L.;
Itzstein, M. v. Carbohydr. Res. 1996, 289, 67-75. (u) Chan, T.-H.; Xin,
Y.-C.; Itzstein, M. v. J. Org. Chem. 1997, 62, 3500-3504. (v) Kuboki, A.;
Sekiguchi, T.; Sugai, T.; Ohta, H. Synlett 1998, 479-482. (w) Kong, D. C.
M.; Itzstein, M. v. Carbohydr. Res. 1998, 305, 323-329.
Figure 3. Determination of C-8 stereochemistry.
This material was recrystallized (acetone/MeOH), and its
structure was confirmed by X-ray crystallography.12
Inversion of the C-4 stereocenter to reveal the natural
configuration of KDN required differentiation of the four
hydroxyls in 3. This was cleanly accomplished by a
tin-catalyzed tosylation reaction (Scheme 2).13 While this
recently reported reaction had only been used for the rapid
monotosylation of the primary hydroxyl of an acyclic 2°, 1°
vicinal diol, both the equatorial and primary hydroxyls of
tetraol 3 were selectively sulfonylated without detection of
any other disulfonylation products. Stirring a suspension of
3 in methylene chloride (0.05 M) with p-toluenesulfonyl
chloride (2.1 equiv), triethylamine (2.1 equiv), and dibutyltin
oxide (0.05 equiv) for 12 h gave an unstable ditosylate that
Org. Lett., Vol. 3, No. 2, 2001
239

After some experimentation, it was found that simply
adding a drop of sulfuric acid to 2 in methanol at 0 °C cleanly
gave methyl glycoside 12 after 3 h (90%, 100% based on
recovered 2), following acetylation of the initially formed
methanolysis product. Longer reaction time or increased
temperature gave several polar acetate cleavage products
which could all be converted to 12 and 2 after peracetylation,
but this lowered the yield slightly and did not significantly
improve the overall conversion.
Final unmasking of the carboxylic acid function was best
achieved using RuO4, formed in situ by adding a catalytic
amount of RuCl3‚3H2O (0.05 equiv) to a 2:2:3 CCl4/CH3-
CN/H2O mixture containing 12 and NaIO4 (12 equiv).5b-e,17
After 3 h at ambient temperature, clean conversion to KDN
pentaacetate methyl glycoside was achieved, isolated as
methyl ester 13 (84%), for which all data (1H NMR; melting
point; IR; HRMS; and optical rotation) were in agreement
with the literature.18,19 The formal synthesis of KDN has thus
been achieved in 45% overall yield from diene diol 6,
employing our convergent ketalization/ring-closing metath-
esis strategy. Global deprotection of 13 has been achieved
previously by moist methanol/sodium methoxide ester
cleavage19a and methyl glycoside hydrolysis (refluxing
AcOH/H2O).3a This efficient and unique entry to KDN
synthesis should make possible the stereocontrolled construc-
tion of various KDN derivatives due to the conformationally
defined bicyclic acetal template and readily differentiated
hydroxyls in the 2,7-anhydro sugar analogue 3. The synthesis
of other sialic acids via this route is presently being pursued
and will be reported in due course.
(5) For examples, see the following: (a) Yamada, T.; Kakinuma, K.;
Oshima, T. Chem. Lett. 1987, 1745-1748. (b) Azam, S.; D’Souza, A. A.;
Wyatt, P. B. J. Chem. Soc., Perkin Trans. 1 1996, 621-627. (c) Arvanitis,
E.; Motevalli, M.; Wyatt, P. B. Tetrahedron Lett. 1996, 37, 4277-4280.
(d) Sloan, M. J.; Kirk, K. L. Tetrahedron Lett. 1997, 38, 1677-1680. (e)
Eguchi, T.; Morita, M.; Kakinuma, K. J. Am. Chem. Soc. 1998, 120, 5427-
5433.
(6) (a) Kolb, H. C.; VanNieuwenhze, M. S.; Sharpless, K. B. Chem. ReV.
1994, 94, 2483-2547. (b) Becker, H.; Sharpless, K. B. Angew. Chem., Int.
Ed. Engl. 1996, 35, 448-451.
Acknowledgment. We thank the NIH [Grant CA74394
(S.D.B.) and CBI Training Grant 5 T32 GM08505 (E.A.V.)]
for generous support of this research. The NIH (1 S10 RR0
8389-01) and NSF (CHE-9208463) are acknowledged for
their support of the NMR facilities of the University of
Wisconsin-Madison Department of Chemistry. We also thank
Michael Kavana for X-ray crystallographic analysis.
(7) Burke, S. D.; Sametz, G. M. Org. Lett. 1999, 1, 71-74.
(8) Kossmehl, G.; Frohberg, H.-C. Chem. Ber. 1986, 119, 50-64.
(9) Grandberg, I. I.; Zuyanova, T. I. Khim. Geter. Soed. 1968, 4, 875-
877.
(10) Sharpless, K. B.; Young, M. W. J. Org. Chem. 1974, 40, 947-
949. Potassium t-butoxide elimination (ref 1) provided 5 in 57% yield from
8 with ∼30% SN2 displacement product.
Supporting Information Available: Experimental pro-
cedures and spectral data for compounds 2-5, 7, 8, and 10-
13; comparison of full characterization for 13 with literature
data; X-ray crystallographic data for 10. This material is
available free of charge via the Internet at http://pubs.acs.org.
(11) For recent reviews, see the following: (a) Schuster, M.; Blechert,
S. Angew. Chem., Int. Ed. Engl. 1997, 36, 2036-2056. (b) Armstrong, S.
K. J. Chem. Soc., Perkin Trans. 1 1998, 371-388. (c) Grubbs, R. H.; Chang,
S. Tetrahedron 1998, 54, 4413-4450. (d) Schrock, R. R. Tetrahedron 1999,
55, 8141-8153.
(12) See Supporting Information.
OL006887L
(13) Martinelli, M. J.; Nayyar, N. K.; Moher, E. D.; Dhokte, U. P.;
Pawlak, J. M.; Vaidyanathan, R. Org. Lett. 1999, 1, 447-450.
(14) For reviews, see the following: (a) David, S.; Hanessian, S.
Tetrahedron 1985, 41, 643-663. (b) Grindley, T. B. AdV. Carbohydr. Chem.
Biochem. 1998, 53, 16-142.
(18) (a) Mononen, I.; Lengstad, B.; Lo¨nngren, J. Acta Chem. Scand. B
1980, 34, 775-776. (b) Nakamura, M.; Takayanagi, H.; Furuhata, K.; Ogura,
H. Chem. Pharm. Bull. 1992, 40, 879-885.
(15) The tin-catalyzed monobenzoylation of various vicinal diols has been
recently reported: (a) Maki, T.; Iwasaki, F.; Matsumura, Y. Tetrahedron
Lett. 1998, 39, 5601-5604. (b) Iwasaki, F.; Maki, T.; Onomura, O.;
Nakashima, W.; Matsumura, Y. J. Org. Chem. 2000, 65, 996-1002.
(16) (a) Huffman, J. W.; Desai, R. C. Synth. Commun. 1983, 13, 553-
557. (b) Torisawa, Y.; Okabe, H.; Ikegami, S. Chem. Lett. 1984, 1555-
1556. (c) Sato, K.-I.; Yoshitomo, A. Chem. Lett. 1995, 39-40. (d) Shimizu,
T.; Hiranuma, S.; Nakata, T. Tetrahedron Lett. 1996, 37, 6145-6148. (e)
Pour, M.; Willis, A. C.; Furber, M.; Mander, L. N. Tetrahedron 1998, 54,
13833-13850.
(19) Data for 13: 1H NMR (CDCl3) δ 5.42 (dd, J ) 5.5, 2.5 Hz, 1H),
5.32 (ddd, J ) 11.5, 10, 5 Hz, 1H), 5.31 (ddd, J ) 6.5, 5.5, 2 Hz, 1H),
4.90 (t, J ) 10 Hz, 1H), 4.71 (dd, J ) 12.5, 2.5 Hz, 1H), 4.15 (dd, J )
12.5, 6.5 Hz, 1H), 4.06 (dd, J ) 10, 2 Hz, 1H), 3.82 (s, 3H), 3.26 (s, 3H),
2.52 (dd, J ) 13, 5 Hz, 1H), 2.12 (s, 3H), 2.08 (s, 3H), 2.04 (s, 3H), 2.02
(s, 3H), 2.00 (s, 3H), 1.84 (dd, J ) 13, 11.5 Hz, 1H); 13C NMR (CDCl3)
δ 170.6 (C), 170.2 (C), 170.00 (C), 169.92 (C), 169.8 (C), 167.1 (C), 98.7
(C), 70.8 (CH), 69.9 (CH), 69.1 (CH), 67.8 (CH), 67.4 (CH), 62.0 (CH2),
52.7 (CH3), 51.3 (CH3), 36.9 (CH2), 21.0 (CH3), 20.8 (CH3), 20.72 (CH3),
20.67 (CH3), 20.6 (CH3); IR (thin film) 2956, 1748, 1373, 1220, 1050 cm-1
;
(17) Carlsen, P. H. J.; Katsuki, T.; Martin, V. S.; Sharpless, K. B. J.
Org. Chem. 1981, 46, 3936-3938.
[R]24 -6.8° (c ) 0.28, CHCl3); mp 115-116 °C; HRMS (FAB) calcd.
D
for C21H30O14Na (M+Na+) 529.1533, found 529.1555.
240
Org. Lett., Vol. 3, No. 2, 2001