From cycloheptatriene to enantiopure sugars: Synthesis of 2-deoxyhexoses

Article abstract of DOI:10.1016/S0008-6215(98)00145-1

meso-Diol 3, prepared from cycloheptatriene, was desymmetrized with Pseudomonas cepacia lipase and isopropenyl acetate to provide enantiopure 4. The latter, through a series of stereocontrolled oxidation reactions, followed by ring cleavage by ozonolysis and oxidative cleavage of a terminal diol with periodate, provided of 2-deoxy-d-xylo-hexose (1) and 2-deoxy-d-arabino-hexose (2), which were characterized as the corresponding alditol pentaacetates. Copyright (C) 1998 Elsevier Science Ltd.

Full text of DOI:10.1016/S0008-6215(98)00145-1

Carbohydrate Research 309 (1998) 331±335
From cycloheptatriene to enantiopure sugars:
synthesis of 2-deoxyhexoses
Carl R. Johnson *, Adam Golebiowski, Janusz Kozak
Department of Chemistry, Wayne State University, Detroit, Michigan 48202-3489, USA
Received 9 March 1998; accepted 4 June 1998
Abstract
meso-Diol 3, prepared from cycloheptatriene, was desymmetrized with Pseudomonas cepacia
lipase and isopropenyl acetate to provide enantiopure 4. The latter, through a series of stereo-
controlled oxidation reactions, followed by ring cleavage by ozonolysis and oxidative cleavage of a
terminal diol with periodate, provided of 2-deoxy-d-xylo-hexose (1) and 2-deoxy-d-arabino-hexose
(2), which were characterized as the corresponding alditol pentaacetates. # 1998 Elsevier Science
Ltd. All rights reserved
Keywords: Lipase; Cycloheptatriene; Ozonolysis; Sodium metaperiodate; 2-deoxy-d-xylo-hexose; 2-deoxy-d-
arabino-hexose
1. Introduction
2-Deoxyhexoses are currently of interest to
many groups [7±13] for their biological activity
[14±17], per se, and for use as analogs in the studies
of various aspects of carbohydrate transport and
metabolism [18±21]. In this note we describe the
syntheses of 2-deoxy-d-xylo-hexose (1) and 2-
deoxy-d-arabino-hexose (2) as examples of our
cycloheptatriene-based approach to highly oxygen-
ated natural products.
Scheme 1 shows synthetic and retrosynthetic
links between these two sugars and cycloheptatriene.
Compound 4 was obtained in very high enan-
tiopurity (>99% ee) from the meso-diol 3 by
Pseudomona cepacia lipase-catalyzed desymme-
trization in the presence of isopropenyl acetate
according to the protocol previously described by
us [6,22]. Protection of the allylic hydroxyl group
of 4 as its benzyloxymethyl (BOM) ether, followed
by alcoholysis of the acetate group and pyr-
idinium dichromate (PDC) oxidation, a€orded the
Enzymes have proven to be practical and e-
cient tools for enantiocontrolled organic synthesis
[1,2]. In the course of our studies on the enantio-
selective synthesis of polyoxygenated natural
products, we have observed that lipases, in parti-
cular, o€er wide opportunities for the generation
of enantiopure intermediates from racemic alco-
hols and prochiral or meso-diols and/or the corre-
sponding esters [3]. Enzymatic desymmetrization of
meso-diols [4,5] opens access to complicated, ste-
reochemically pure products including sugars [6].
This paper presents a part of our studies on the
stereocontrolled synthesis of polyoxygenated com-
pounds involving ®ve-, six- and seven-membered
polyenes as achiral starting materials.
* Corresponding author. Fax: 313-577-2554.
0008-6215/98/$Ðsee front matter # 1998 Elsevier Science Ltd. All rights reserved
PII S0008-6215(98)00145-1

332
C.R. Johnson et al./Carbohydrate Research 309 (1998) 331±335
in a diol that was protected as its acetonide deri-
vative 8. Ozonolysis of 8, followed by reductive
workup a€orded protected heptitol 9, which, after
hydrogenolytic removal of the BOM-ether with
Degussa palladium catalyst [24] and cleavage of the
resulting vicinal diol with NaIO4 supported on
silica gel [25], o€ered 2-deoxy-d-xylo-hexose as its
open-chain, protected derivative 10.
The free sugar exists as an anomeric mixture of
both pyranose and furanose forms, and its 1,6-
anhydro derivative is very easily formed [26]. For
these reasons we decided to characterize this target
by conversion to the known penta-O-acetyl 2-deoxy-
d-xylo-hexitol (11) [27]. Sodium borohydride
reduction of aldehyde 10, followed by acidolysis
and peracetylation of the resulting pentaol, a€or-
ded 11, which was identical in all respects to the
compound reported by Moore et al. [27].
2-Deoxy-d-arabino-hexopyranose (`2-deoxy-d-
glucose', 2) was synthesized using the same starting
monoacetate 4 (Scheme 3). Protection of the allylic
hydroxyl group as its tert-butyldiphenylsilyl
(TBDPS) ether, anti-directed cis-hydroxylation
[28,29] and protection of the resulting 1,2-diol,
followed by chemoselective cleavage of the tert-
butyldimethylsilyl ether and Swern oxidation of the
thus formed alcohol, o€ered enone 12 in high (ca.
60%) yield [22]. DIBAL-H reduction of 12 gave a
Scheme 1.
ꢀ,ꢁ-unsaturated ketone 5 [22] in ca. 90% overall
yield (Scheme 2). Enone 5 was transformed into the
silyloxydiene 6, which upon treatment with m-
CPBA (Rubottom procedure) [23] yielded ꢀ-oxy-
genated enone 7. DIBAL-H reduction of 7 with
removal of the Me3Si group during workup resulted
Scheme 3. (a) i. TPSCl, imidazole, DMF; ii. OsO4, N-
methylmorpholine N-oxide, THF±H2O; iii. 2,2-dimethoxy-
propane, TsOH; iv. 0.05 N KOH, MeOH; v. MsCl, Et3N,
CH2Cl2; vi. pyridinium tosylate, MeOH; vii. PDC, CH2Cl2;
(b) DIBAL-H, Et2O; (c) i. O3, 78 ꢀC, Me2S, ii. NaBH4,
MeOH; (d) NaIO4/SiO2, CH2Cl2; (e) i. Dowex-50 (H+),
MeOH; ii. Bu4NF±THF; (f) Ac2O±pyridine; (g) i. 6 N HCl,
THF, ii. Ac2O±pyridine.
Scheme 2. (a) i. BOMCl, 2-Pr2EtN, CH2Cl2; ii. 0.05 N KOH,
MeOH; iii. PDC, CH2Cl2; (b) TMSOTf, Et3N; (c) m-CPBA,
CH2Cl2; (d) i. DIBAL-H, Et2O, 78 ꢀC; ii. 2,2-dimethoxy-
propane, TsOH; (e) i. O3, CH2Cl2, 78 C, Me2S; ii. NaBH4,
MeOH; (f) i. H2, Pd/C, AcOEt; ii. NaIO4/SiO2, CH2Cl2; (g) i.
NaBH4, MeOH; ii. HCl (aq), MeOH; iii. Ac2O±pyridine.
ꢀ

C.R. Johnson et al./Carbohydrate Research 309 (1998) 331±335
333
1:1 mixture of diastereoisomeric allylic alcohols 13.
Ozonolysis of 13, followed by reductive workup
with sodium borohydride, a€orded a mixture of
triols 14 which, without separation, was subjected
to one-carbon degradation at the vicinal diol func-
tionality with the NaIO4/SiO2 system [25]. Our
approach to the 2-deoxyglucose derivative 16 was
executed starting from aldehyde 15; the latter upon
treatment with Dowex-50 resin in methanol and
subsequent cleavage of the tert-butyldiphenylsilyl
protection a€orded crude methyl 2-deoxy-d-ara-
bino-hexopyranoside (16). For analytical purposes
this material was peracetylated to produce the
desired triacetate 17 as a mixture of ꢀ- and ꢁ-
anomers [31] `enriched' with another major deriva-
tive (1H NMR spectroscopy suggested the methyl
furanoside). For this reason the aldehyde 15 was
reduced with sodium borohydride in methanol,
totally deprotected with 6 N hydrochloric acid in
THF, and acetylated, to give penta-O-acetyl-2-
deoxy-d-arabino-hexitol (`2-deoxy-d-glucitol pen-
taacetate') 18. The latter was found to be identical
to the literature compound in all respects [31].
chromatographed on silica gel (3:7 EtOAc±petro-
leum ether) to give 9 (178 mg, 0.379 mmol, 82%
yield) as a clear oil: H NMR (CDCl3): ꢂ 7.42±7.25
1
(m, 5 H); 4.89 (1/2 ABq J 7.01 Hz, 1 H); 4.78 (1/2
ABq J 7.06 Hz, 1 H); 4.74 (1/2 ABq J 11.8 Hz, 1 H);
4.60 (1/2 ABq J 11.8 Hz, 1 H); 4.10±3.42 (m, 8 H);
2.75 (bs, 2 H); 1.85 (dd1/2 ABq J 6.04, 12.32,
14.12 Hz, 1 H); 1.75 (dd1/2 ABq J 5.62, 7.63,
14.06 Hz, 1 H); 1.40 (s, 3 H); 1.38 (s, 3 H); 0.90 (s, 9
H); 0.10 (s, 6 H); 13C NMR (CDCl3): ꢂ 137.2; 128.7
(2C); 128.1 (2C); 128.0; 109.0; 95.1; 79.8; 79.2; 77.4;
70.2; 69.0; 65.6; 62.9; 35.5; 27.2; 26.0; 18.2; 4.3 4.6
Penta-O-acetyl-2-deoxy-d-xylo-hexitol (11).Ð
Diol 9 was dissolved in 80 mL of ethyl acetate,
and Degussa 10% palladium catayst (50 mg) was
added. The sample was hydrogenated at room
temperature for 16 h. The catalyst was then ®ltered
o€ and the solvent was evaporated under reduced
pressure to yield the crude intermediate triol as a
clear oil. Sodium periodate (162 mg, 0.757 mmol)
dissolved in water (0.6 mL) was dropped into a
vigorously stirred suspension of silica gel (4 g) in
dichloromethane (15 mL) [24]. The crude triol
(132 mg, 0.383 mmol) dissolved in dichloromethane
(2 mL) was added, and the reaction mixture was
stirred for 1 h. The reaction mixture was ®ltered,
and the silica gel was washed with dichloro-
methane (2Â20 mL). Combined ®ltrates were con-
centrated in vacuo, to give (3S,4R,5R)-3-(tert-butyl-
dimethylsilyloxy)-6-hydroxy-4,5-(isopropylidene-
dioxy)hexanal (10) (87 mg, 0.27 mmol, 72%) as a
clear oil. The aldehyde was immediately carried
forward to the next step.
2. Experimental
General.ÐIntermediates were characterized by
1
clean H and 13C NMR spectra and by conversion
to the known alditol acetates 11 and 18. The
structures of the latter were established by favor-
able comparison of optical rotation and NMR
data with values in the literature.
(2R,4S,5R,6R)-2-(Benzyloxymethoxy)-4-(tert-
butyldimethylsilyloxy)-5,6-(isopropylidenedioxy)hept-
ane-1,7-diol (9).ÐOle®n 8 [22] (200 mg, 0.461 mmol)
was dissolved in 1:1 methanol±dichloromethane
(5 mL). A stream ꢀof ozone was passed through the
solution at 78 C until saturation was reached
(blue color). The solution was ¯ushed with oxygen
until the blue color disappeared. Methyl sul®de
(0.5 mL), followed by solid sodium borohydride
(35 mg, 0.92 mmol), was added, and the cooling
bath was removed. After stirring at room tempera-
ture for an additional 0.5 h, the reaction mixture
was poured into diethyl ether (50 mL) and washed
with satd aq solutions of NaHCO3 (10 mL), NH4Cl
(10 mL) and NaCl (10 mL). The combined aqu-
eous phases were extracted with diethyl ether
(2Â10 mL). The combined organic extracts were
dried over MgSO4, and solvent was removed
under reduced pressure to give a clear oil that was
Aldehyde 10 (87 mg, 0.27 mmol) was dissolved in
10 mL of methanol, and the solution was cooled to
ꢀ
20 C. Sodium borohydride (21 mg, 0.54 mmol)
was added, and the reaction mixture was main-
ꢀ
tained at 20 C for 30 min. An excess of the
hydride was then quenched with acetone, and the
mixture was diluted with 50 mL of diethyl ether.
The ether solution was washed with satd NH4Cl
(10 mL), brine (10 mL), dried over MgSO4, ®ltered
and evaporated. The crude diol was dissolved in
dry THF (10 mL) and treated with concentrated
aqueous HCl (2 mL) for 16 h. The mixture was
evaporated to dryness to give the crude pentaol,
which was dissolved in dry pyridine (5 mL) and
treated with acetic anhydride (5 mL) in the pre-
sence of the catalytic amount of DMAP. After 24 h
stirring the reaction mixture was poured into die-
thyl ether (50 mL) and washed with 1 N HCl,
(10 mL) satd aq NaHCO3 (10 mL), and brine

334
C.R. Johnson et al./Carbohydrate Research 309 (1998) 331±335
(10 mL). The ether solution was dried over MgSO4,
®ltered and evaporated to give crude pentaacetate
11. The hexitol pentaacetate was puri®ed by column
chromatography using 20% EtOAc in petroleum
Penta-O-acetyl-2-deoxy-d-arabino-hexitol
deoxy-d-glucitol pentaacetate) (18).ÐEnol 13
(201 mg, 0.459 mmol) was dissolved in a 1:1
(2-
methanol±dichloromethane mixture (6 mL).
stream of ozone was passed through the solution at
A
ether as an eluent to yield 78 mg (76%) of optically
4.0 (c
20
d
ꢀ
[30] and spectroscopically [27] pure 11: ‰ꢀŠ
78 C, until saturation was reached (blue color).
20
1, CHCl3), lit [30]. (for antipode) ‰ꢀŠ +3.7 (c 4,
The solution was ¯ushed with oxygen untill the
blue color disappeared. Methyl sul®de (0.5 mL),
followed by solid sodium borohydride (87 mg,
2.3 mmol) was added, and the cooling bath was
removed. After stirring at room temperature for
additional 0.5 h, the reaction mixture was poured
into diethyl ether (50 mL) and washed with satd aq
solutions of NaHCO3 (10 mL), NH4Cl (10 mL),
and NaCl (10 mL). The combined aq phases were
washed with diethyl ether (2Â10 mL). The com-
bined extracts were dried over MgSO4, ®ltered and
concentrated under reduced pressure to give
(2RS,4R,5S,6R)-4-(tert-butyldiphenylsilyloxy)-
4,5-(isopropylidenedioxy)-1,2,7-heptanetriol (14)
(216 mg, 0.456 mmol, 100% yield) as a clear oil
that was immediately carried forward to the next
step.
Sodium periodate (194 mg, 0.907 mmol) dis-
solved in water (1.5 mL) was added dropwise into a
vigorously stirred suspension of silica gel (4 g) in
dichloromethane (18 mL) [24]. Triol 14 (216 mg,
0.456 mmol) dissolved in dichloromethane (2 mL)
was added, and the reaction mixture was stirred for
1 h. The reaction mixture was ®ltered, and the silica
gel pad was washed with dichloromethane
(2Â10 mL). The combined ®ltrates were con-
centrated in vacuo to give crude (3R,4S,5R)-3-
(tert-butyldiphenylsilyloxy)-6-hydroxy-4,5-(iso-
propylidenedioxy)hexanal (15) (148 mg, 0.34 mmol,
74%) as a colorless oil, which was used immediately
in the next step.
d
1
CHCl3); H NMR (CDCl3): ꢂ 5.31±5.16 (m, 3 H);
4.34 (d1/2ABq, J 3.74, 12.2 Hz, 1 H); 4.05 (t, J
6.2 Hz, 2 H); 3.95 (d1/2ABq, J 5.6, 12.0 Hz, 1
H); 2.08 (s, 3 H); 2.064 (s, 3 H); 2.061 (s,3 H);
2.02 (s, 6 H); 1.90±1.76 (m, 2 H); 13C NMR
(CDCl3): ꢂ 170.9; 170.5; 170.2; 170.1; 170.0; 71.3;
69.4; 68.6; 62.0; 60.1; 29.9; 20.9 (2C); 20.8; 20.7;
20.6.
(1RS,4R,5S,6R)-6-(tert-Butyldiphenylsilyloxy)-
4,5-(isopropylidenedioxy)-2-cyclohepten-1-ol (13).Ð
Enone 12 [22] (200 mg, 0.459 mmol) was dissolved
in dry diethyl ether (30 mL) and cooled under
ꢀ
argon atmosphere to 78 C. 1.5 M DIBAL-H in
toluene (760 mL, 1.14 mmol) was added, and the
reaction mixture was stirred for 15 min. An excess
of the hydride was then quenched with methanol
(1 mL), and satd aq sodium-potassium tartrate
(20 mL) was added. The reaction mixture was vig-
orously stirred at room temperature until the alu-
mina salts were completely dissolved. The phases
were separated, and the etheral solution was
washed with satd NH4Cl (10 mL) and brine
(10 mL), dried over MgSO4, ®ltered and evapo-
rated. The resulting colorless oil was puri®ed with
column chromatography (1:9 EtOAc±petroleum
ether) to give 201 mg (95%) of 13 as a mixture of
1
two diastereoisomers (2:1 ratio). 13a (major): H
NMR (CDCl3): ꢂ 7.80±7.62 (m, 4 H); 7.52±7.30 (m,
6 H); 5.44 (s, 2 H); 4.74 (d, J 6.66 Hz, 1 H); 4.35
(dd, J 6.00, 4.52 Hz, 1 H); 4.21 (dd, J 6.60, 6.60 Hz,
1 H); 4.11 (ddd, J 8.71, 6.60, 1.82 Hz, 1 H); 2.01
(dd1/2ABq, J 4.80, 9.00, 13.80 Hz, 1 H); 1.87 (dd1/
2ABq, J 1.81, 6.90, 13.82 Hz, 1 H); 1.36 (s, 3 H);
1.30 (s, 3 H); 1.09 (s, 9 H); 13C NMR (CDCl3): ꢂ
136.1; 136.0; 134.1; 133.6; 131.0; 129.8; 129.6;
129.0; 127.6; 127.4; 108.5; 82.1; 74.3; 69.4; 66.6;
Aldehyde 15 (148 mg, 0.335 mmol) was dissolved
in 6 mL of absolute methanol and cooled to
ꢀ
20 C. Sodium borohydride (25 mg, 0.67 mmol)
was added, and reaction mixture was kept at
ꢀ
20 C for 15 min. An excess of the hydride was
then quenched with acetone (1 mL), and the mix-
ture was diluted with 50 mL of diethyl ether. The
ether solution was washed with satd aq NH4Cl
(10 mL) and brine (10 mL), dried over MgSO4, ®l-
tered and evaporated. The crude diol was dissolved
in dry tetrahydrofuran (10 mL) and treated with
concentrated aqueous HCl (2 mL) for 16 h. The
mixture was then evaporated to dryness, and the
crude pentaol was dissolved in dry pyridine (4 mL)
and treated with acetic anhydride (4 mL) in the
1
39.2; 27.4; 27.0.; 25.3; 19.3. 13b (minor): H NMR
(CDCl3): ꢂ 7.80±7.60 (m, 4 H); 7.50±7.30 (m, 6 H);
5.53 (s, 2 H); 4.82 (d, J 6.00 Hz, 1 H); 4.31 (dd, J
6.60, 6.60 Hz, 1 H); 3.89±3.68 (m, 2 H); 2.08±1.76
(m, 2 H); 1.67 (bs, 1 H); 1.35 (s, 3 H); 1.32 (s, 3 H);
1.10 (s, 9 H); 13C NMR (CDCl3): ꢂ 136.2; 135.9;
133.9; 133.5; 130.1; 129.8; 129.7; 129.6; 127.6;
127.4; 108.5; 82.6; 73.6; 70.6; 67.6; 39.7; 27.5; 27.0.;
25.2; 19.2.

C.R. Johnson et al./Carbohydrate Research 309 (1998) 331±335
335
presence of a catalytic amount of DMAP. After
stirring for 48 h the reaction mixture was poured
into diethyl ether (50 mL) and washed with 1 N
HCl (10 mL), satd aq NaHCO3 (10 mL) and brine
(10 mL). After drying over MgSO4, the etheral
solution was ®ltered and evaporated to give crude
pentaacetate 18. The latter was puri®ed by col-
umn chromatography using 2:8 EtOAc±petroleum
[10] M.E. Haque, T. Kikuchi, K. Kanemitsu, and Y.
Tsuda, Chem. Pharm. Bull., 35 (1987) 1016±1029.
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Chem., 2 (1983) 99±103.
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(1986) 1610±1620.
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Carbohydr. Res., 68 (1979) 33±41.
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ched-Chain Sugars, in W. Pigman and D. Horton
(Eds.), The Carbohydrates, Chemistry and Bio-
chemistry, 2nd ed., Vol. 1B, Academic Press, New
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ether as an eluent to give pure product 18 [31]
+36 (c 1.0, CH2Cl2); lit
20
d
(103 mg, 82%): ‰ꢀŠ
25
d
[31]. ‰ꢀŠ
+34.6 (c 0.1, CH2Cl2); 1H NMR
(CDCl3): ꢂ 5.33±5.20 (m, 2 H); 5.09 (ddd, J 2.71,
4.60, 8.00 Hz, 1 H); 4.20 (d1/2ABq, J 2.60,
12.59 Hz, 1 H); 4.11 (d1/2ABq, J 4.68, 12.49 Hz, 1
H); 4.02 (t, J 6.40 Hz, 2 H); 2.11 (s, 3 H); 2.034 (s, 3
H); 2.027 (s, 3 H); 2.024 (s, 3 H); 2.010 (s, 3 H);
1.90±1.75 (m, 2 H); 13C NMR (CDCl3): ꢂ 170.7;
170.4; 170.1; 169.7 (2C); 70.5; 68.3; 67.6; 61.8; 60.2;
30.1; 20.7 (2C); 20.56 (3C).
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41±46.
Acknowledgement
This work was supported by a grant from the
National Science Foundation (CHE-9801679).
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