Total syntheses of aminomethyl-C-dideoxyglycopyranosides and their quinamides

Article abstract of DOI:10.1016/S0040-4039(03)01692-7

Lewis acid promoted cyclization of homoallylic alcohol 1 with acetal 2 gave 4-chloro-2-phthalimidomethyl-6-methyltetrahydropyrans. Their dehydrochlorination produced two regioisomeric dihydropyrans. Subsequent cis- and trans-dihydroxylation gave four race

Full text of DOI:10.1016/S0040-4039(03)01692-7

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 6587–6590
Total syntheses of aminomethyl-C-dideoxyglycopyranosides and
their quinamides
Dmitriy E. Gremyachinskiy, Vyacheslav V. Samoshin and Paul H. Gross*
Department of Chemistry, University of the Pacific, Stockton, CA 95211, USA
Received 2 July 2003; accepted 6 July 2003
Abstract—Lewis acid promoted cyclization of homoallylic alcohol 1 with acetal 2 gave 4-chloro-2-phthalimidomethyl-6-methyltet-
rahydropyrans. Their dehydrochlorination produced two regioisomeric dihydropyrans. Subsequent cis- and trans-dihydroxylation
gave four racemic dihydroxy-6-methyl-2-phthalimidomethyl tetrahydropyrans. They were deprotected and N-acylated with a
chiral quinic acid lactone, producing a library of four diastereomeric mixtures of novel C-pseudodisaccharides, which were
separable after derivatization.
©
2003 Elsevier Ltd. All rights reserved.
C-Glycosides, chemically and enzymatically stable ana-
logues of carbohydrates, may compete in cell surface
adhesion, inhibit carbohydrate-processing enzymes and
interfere in the biosynthesis of specific cell surface
carbohydrates, and are therefore potential therapeutic
agents against HIV and other infections, against cancer,
their quinoylation. Quinic acid is an important struc-
tural component in a number of naturally occurring
biologically active compounds which exhibit HIV-inte-
9
10
grase inhibition,1 as well as hypocholesterolemic,
1
12
hepatoprotective and antioxidative activities. Com-
mercially available quinic acid is an attractive starting
material for syntheses of shikimic acid and other chiral
1
–3
diabetes and other metabolic disorders.
C-Glycopy-
13
ranosides with an aminomethyl group on the anomeric
compounds, such as carbasugars. A combination of
racemic aminomethyl C-glycosides with chiral quinic
acid may directly yield biologically active chiral
compounds.
3
carbon may be potent inhibitors for glycosidases. C-
Glycosides are building blocks of polyether antibiotics
1
and toxins. The great majority of methods developed
1,2
for the synthesis of C-glycosides start from natural
sugars, mostly -glucose, -mannose and -galactose,
which are commercially available in multigram quanti-
D
D
D
Acid-catalyzed reactions between homoallylic alcohols
and aldehydes or acetals have been used before for the
preparation of 2,6-disubstituted di- and tetra-
4
ties. Other
rides are very expensive and available only on a
D-monosaccharides and all L-monosaccha-
8,14
hydropyran derivatives.
We chose an expandable
4
milligram scale. Moreover,
-idose exist in appreciable proportions as their 1,6-
D
-gulose,
D
-altrose and
two-component scheme of cyclization with a possibility
of various functional groups in readily available start-
ing compounds. Use of phthalimido derivatives allowed
for syntheses of (protected) aminomethyl C-glycopyran-
osides (Scheme 1).
D
anhydrides with essentially different chemical behav-
5
ior. Here we report the total syntheses of partially
functionalized b-C-glycopyranosides, related to 2,4-
6,7
and 4,6-dideoxyhexoses, found as cardiac glycosides.
These C-glycosides are tetrahydropyrans, obtained
from homoallylic alcohols and acetals by a Lewis acid
promoted cyclization, followed by dehydrohalogenation
and subsequent double bond functionalization. (Some
parts of this work have been reported previously ). A
subsequent use of these building blocks for the synthe-
ses of di- and oligosaccharide mimics is illustrated by
Cyclizations of this type furnish exclusively cis-2,6-dis-
8,14
ubstituted tetrahydropyrans
configuration of the projected C-glycopyranosides.
Most C-glycoside syntheses provide a-products. The
corresponding to the b-
2
8
new stereocenter C(6) is entirely determined by the
configuration of the existing stereocenter in the
homoallylic alcohol. Chiral homoallylic alcohols would
give enantiomerically pure tetrahydropyrans, and
finally C-glycosides, while we obtained racemic
aminomethyl C-glycosides, subsequently acylated with
the chiral lactone of quinic acid (Scheme 1), and sepa-
*
Corresponding
author.
Fax:
+1-209-946-2607;
e-mail:
vsamoshin@uop.edu
0
040-4039/$ - see front matter © 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0040-4039(03)01692-7

6
588
D. E. Gremyachinskiy et al. / Tetrahedron Letters 44 (2003) 6587–6590
Scheme 1. Synthesis of aminomethyl-C-glycosides (3–10: stereoisomeric mixtures; 11–22: racemic mixtures; Phth=phthaloyl). (a)
SnCl , CH Cl , −55°C, 82%; (b) DBU, LiCl, Py, reflux, 79%; (c) urea–H O , TFAA, 93%; (d) TFAA, H O/THF, 60°C, 74%; (e)
4
2
2
2
2
2
OsO , NMO, 64%; (f) (1) Me NH, MeOH, H O, (2) H SO , H O, (3) NH OH, 80–86% (15–18: R=H); (g) Ac O, DMAP, Py,
4
2
2
2
4
2
4
2
5
1–85% (19–22: R=Ac); (h) 24, DMA, 70°C, 58–77%; (i) acetone, p-TsOH, reflux, 86%; (j) BnNH , DMA, 55°C, 72%.
2
1
7
rated as derivatives of diastereomeric quinamides
trans-diaxially, allowed for direct synthesis of a two-
component trans-diol mixture 11, 12, separated by
(
Scheme 2).
‡
column chromatography (51 and 23%, respectively).
The starting materials 1 and 2 were prepared as
After cis-dihydroxylation (OsO
,6, only compounds 13 and 14 were isolated by
column chromatography (SiO , CH Cl /iPrOH 20/1; 45
and 19%, respectively). This stereoselectivity is worth
of additional investigation.
4
/NMO) of the mixture
15
5
described earlier. Acid promoted cyclization of these
compounds at −55°C in CH Cl solution with SnCl
2
2
2
2
2
4
§
(
Scheme 1) gave chlorotetrahydropyrans 3 and 4 (5:1,
†
separable by column chromatography). The alkenes 5,
6
were obtained as a 2:1 mixture (by NMR) by heating
Thus, we obtained a series of four racemic phthalimido-
of the mixture 3, 4 with DBU in pyridine in presence of
LiCl, which facilitated isomerization of equatorial into
axial halogen, more suitable for elimination. Epoxida-
tion of the alkene mixture with urea–H O complex in
protected aminomethyl C-dideoxyglycopyranosides 11–
1
8
1
4, which produced with Me NH aq.
the
2
dimethylammonium salts of phthalamic acids. They
were hydrolyzed after evaporation of excess Me NH by
heating with aq. H SO (70°C), followed by extraction
2
2
1
6
2
the presence of CF COOH produced an epoxide mix-
3
2
4
ture 7–10 (93%), which was difficult to separate. How-
ever, the well known tendency of epoxides to open
‡
§
Cpd 11: mp 187–188°C; cpd 12: mp 162–164°C.
Cpd 13: mp 190–191°C; cpd 14: mp 193–195°C.
†
Cpd 3: mp 146–148°C; cpd 4: mp 121–122°C.

D. E. Gremyachinskiy et al. / Tetrahedron Letters 44 (2003) 6587–6590
6589
of phthalic acid with CH Cl and Et O. Neutralization
Generally, separation of diastereomeric pairs 26–33
could only be achieved via their derivatives (Scheme 2).
Thus, the trans-dihydroxy aminomethyl C-glycosides
26,27 were separated as their O-acetyl derivatives by
2
2
2
by NH aq. and subsequent evaporation followed by
3
column chromatography (SiO ; CH Cl /MeOH/NH
2
2
2
3
aq.=49/49/2) gave compounds 15–18 (80–86%), char-
acterized and analyzed as their N-acetyl- and/or N,O-
flash chromatography (SiO , EtOAc/hexane, 5/1) to
2
¶
triacetyl derivatives, and used as building blocks for
produce 34 (or 35) (7%), 35 (or 34) (28%), and 34+35
(32%).** Quinamides 32,33 were isopropylidenated,
and the mixture 36,37 was enriched with one of the
pseudodisaccharide syntheses. Acylation of benzyl-
amine with the isopropylidenated g-lactone of quinic
1
9
1
acid 24 provided us with H NMR chemical shifts and
stereoisomers (9:1) by column chromatography (SiO ,
2
††
coupling constants for the quinoyl part of compound
CH Cl /iPrOH 20/1).
2 2
2
5. Similarly we converted racemic C-glycosides 15–18
into their quinamides 26–33 (i.e. into diastereomeric
All isolated compounds gave satisfactory elemental
analyses, and MS, IR, H and C NMR data.
ꢀ
ꢀ
1
13
C-pseudodisaccharides; Scheme 1).
*
*
25
Cpd 34 (or 35): oil, [h]D =−51.5 (c 1.65, CCl ). IR (neat): 3400,
4
−
1 1
1
760, 1680, 1550, 1380, 1250 cm
. H NMR (CDCl ): l 1.13 (d,
3
J=6.0 Hz, 3H, CH ), 1.47 (s, 3H, CH ), 1.49 (s, 3H, CH ), 1.59 (dt,
3
3
3
A
J=14.8, 2.2 Hz, 1H, H-5e ), 1.60 (dd, J=13.2, 12.1 Hz, 1H,
H-2a ), 1.70 (ddd, J=14.6, 11.5, 3.3 Hz, 1H, H-5a ), 2.02 (s, 3H,
B
A
COCH ), 2.06 (s, 3H, COCH ), 2.08 (s, 3H, COCH ), 2.10 (s, 3H,
3
3
3
B
COCH ), 2.16 (ddd, J=13.5, 4.4, 2.5 Hz, 1H, H-2e ), 2.46 (dd,
3
B
J=16.5, 4.4 Hz, 1H, H-6a ), 2.52 (ddd, J=14.8, 11.3, 4.4 Hz, 1H,
A
B
CH N ), 2.92 (ddd, J=16.8, 2.5, 2.5 Hz, 1H, H-6e ), 3.68 (m, 2H,
2
A
A
A
CH N , H-2 ), 3.79 (m, 1H, H-6 ), 3.97 (dd, J=8.0, 5.8 Hz, 1H,
2
B
B
H-4 ), 4.37 (m, J=4.7, 2.5 Hz, 1H, H-5 ), 4.52 (d, J=3.0 Hz, 1H,
H-3 ), 4.86 (q, J=3.0 Hz, 1H, H-4 ), 5.25 (ddd, J=12.1, 7.7, 4.7
A
A
B
13
Hz, 1H, H-3 ), 6.58 (dd, J=7.7, 4.4 Hz, 1H, NH). C NMR
CDCl ): l 20.89, 21.09, 21.13, 21.29, 25.90, 28.13, 28.17, 33.09,
(
3
3
1
6.81, 38.36, 65.45, 67.01, 68.74, 70.68, 71.34, 73.17, 76.62, 80.40,
09.11, 169.75, 169.90, 170.04, 171.21, 171.32. Anal. C25H37NO12
(
543.57). Calcd (%): C, 55.24; H, 6.86; N, 2.58. Found (%): C,
5
5
5.03; H, 7.02; N, 2.53. MS: m/z calcd for C25H38NO12 (M+1)
2
5
44.24, found 544.3. Cpd 35 (or 34): oil, [h]D =−16.73 (c 1.15,
Scheme 2. Separation of diastereomeric mixtures of quina-
mides as isopropilidene-tetra-O-acetyl or diisopropilidene
−
1 1
CCl ). IR (neat): 3200, 2780, 1740, 1680, 1440, 1260, 900 cm . H
4
NMR (CDCl ): l 1.19 (d, J=6.0 Hz, 3H, CH ), 1.31 (s, 3H, CH ),
1.73 (m, 2H, H-5a , H-5e ), 2.00 (dd, J=14.3, 11.5, 1H, H-2a ),
3
3
3
B
derivatives. (a) Ac O, DMAP, Py; (b) 2-methoxypropene,
A
A
2
20
p-TsOH, DMF.
2
2
.08 (s, 3H, COCH ), 2.12 (s, 3H, COCH ), 2.13 (s, 3H, COCH ),
3 3 3
B
.15 (s, 3H, COCH ), 2.26 (dd, J=16.2, 4.9 Hz, 1H, H-6a ), 2.36
3
¶
B
Cpd 19: mp 142–144°C; cpd 20: mp 143–144°C; cpd 21: mp 152–
54°C; cpd 22: oil.
The azeotropically dried (PhMe) aminodiol 15, 16, 17, or 18 (1.4 g,
.4 mmol) with 24 (1.8 g, 8.4 mmol) in 1 ml of DMA was heated
(ddd, J=14.0, 4.4, 2.2 Hz, H-2e ), 2.71 (ddd, J=16.2, 2.5, 2.5 Hz,
1H, H-6e ), 2.97 (ddd, J=13.7, 7.7, 6.0 Hz, CH N ), 3.47 (ddd,
J=13.5, 6.6, 6.6 Hz, 1H, CH N ), 3.76 (t, J=7.7 Hz, 1H, H-2 ),
3.81 (m, 1H, H-6 ), 4.10 (dd, J=7.7, 5.8 Hz, 1H, H-4 ), 4.42 (dt,
J=4.7, 2.8, 2.8 Hz, 1H, H-5 ), 4.64 (d, J=3.3 Hz, 1H, H-3 ), 4.93
(q, J=3.0 Hz, 1H, H-4 ), 5.16 (ddd, J=11.8, 7.7, 4.4 Hz, 1H,
H-3 ), 6.52 (t, J=6.3 Hz, 1H, NH). C NMR (CDCl ): l 20.88,
B
A
1
2
ꢀꢀ
A
A
2
A
B
8
B
A
with stirring at 70°C for 48 h, and was kept at rt for 48 h. DMA
was evaporated in vacuo. The residual yellow oil was analyzed by
TLC and was chromatographed (CH Cl :MeOH:NH OH=95:16:2)
A
B
13
2
2
4
3
to give, respectively, 26/27 (58%; oil), 28/29 (70%; oil), 30/31 (64%;
colorless cryst.), or 32/33 (77%; oil). One of the diastereomers 30 or
21.12, 21.16, 21.23, 21.30, 25.63, 27.93, 31.62, 33.12, 34.08, 38.95,
65.94, 67.15, 68.64, 70.43, 71.79, 72.70, 76.42, 80.49, 109.06, 169.54,
169.58, 170.02, 170.71, 171.15. Anal. C25H37NO12 (543.57). Calcd
(%): C, 55.24; H, 6.86; N, 2.58. Found (%): C, 55.41; H, 7.11; N,
2
5
3
1 crystallized from iPrOH (16%): mp 201–202°C; [h] =−69 (c 0.9,
D
MeOH). IR (KBr): 3580, 3500, 3380, 2900, 2450, 1640, 1530, 1200,
−
1
1
A
9
1
1
3
00 cm
.
H NMR (CD OD): l 1.12 (d, 3H, J=6.3 Hz, CH ),
2.71. MS: m/z calcd for C25H38NO12 (M+1) 544.24, found 544.3.
3
3
B
A
††
1
.28 (s, 3H, CH3 ), 1.45 (ddd, 1H, J=14.2, 11.5, 2.8 Hz, H-5a ),
.52 (s, 3H, CH-3 ), 1.61 (br s, 1H, OH), 1.80 (ddd, 1H, J=14.2,
.2, 2.4 Hz, H-5e ), 2.09 (m, 2H, H-2a , H-6a ), 2.26 (dd, 1H,
J=15.5, 5.6 Hz, H-6e ), 2.43 (dd, 1H, J=15.5, 2.5 Hz, H-2e ), 3.17
For the predominant diastereomer 36 or 37: H NMR (CDCl ): l
3
B
1.24 (d, J=6.3 Hz, 3H, CH3A), 1.36 (s, 6H, 2C(CH ) ), 1.48 (s, 1H,
3 2
A
B
B
CCH ), 1.52 (s, 1H, CCH ), 1.70 (ddd, 1H, J=15.4, 11.8, 4.1 Hz,
3
3
B
B
A
B
B
A
H-3a ), 2.06 (m, 3H, H-2a ,6a ,3e ), 2.28 (ddd, 1H, J=15.1, 5.2,
1.7 Hz, H-6e ), 2.46 (dd, 1H, J=15.7, 2.5 Hz, H-2e ), 3.12 (ddd,
1H, J=13.5, 7.7, 4.4 Hz, CH N ), 3.40 (m, 2H, H-5 , OH-1), 3.58
(m, 2H, H-6 , CH N ), 3.72 (m, 1H, H-2 ), 3.84 (br d, J=2.2 Hz,
2
1H, H-5 ), 4.18 (ddd, 1H, J=6.9, 3.0, 1.4 Hz, H-4 ), 4.36 (ddd, 1H,
J=4.4, 4.4, 1.9 Hz, H-4 ), 4.59 (m, 1H, J=6.3, 2.8 Hz, H-3 ), 4.72
(s, 1H, OH-3), 7.34 (t, 1H, J=5.77 Hz, NHCO). C NMR
A
B
B
(
dd, 1H, J=9.7, 3.1 Hz, H-3 ), 3.28 (ddd, 1H, J=14.6, 4.8, 3.0 Hz,
A
A
A
A
CH N ), 3.51 (br s, 1H, OH), 3.71 (dd, 1H, J=9.7, 3 Hz, H-2 ),
2
2
A
B
A
A
A
3
(
.87 (dd, 1H, J=14.6, 3.0 Hz, CH N ), 3.90 (m, 1H, H-5 ), 3.92
2
A
B
A
m, 1H, J=11.5, 6.3, 2.4 Hz, H-6 ), 4.14 (m, 1H, J=3.2, 3.1, 2.8
A
B
B
B
Hz, H-4 ), 4.16 (m, 1H, J=6.6, 3.6 Hz, H-4 ), 4.28 (br s, 1H, OH),
B
13
13
3
.5, 2.5 Hz, H-3 ), 7.49 (t, 1H, J=4.8, 3.0 Hz, NH). C NMR
(
CDCl ): l 21.46, 25.92, 28.49, 35.71, 40.26, 41.08, 42.23, 68.43,
(CDCl ): l 18.65, 24.28, 26.25, 26.95, 28.27, 30.41, 34.36, 36.96,
3
3
6
8.63, 69.01, 70.67, 74.92, 75.05, 75.75, 81.34, 109.70, 178.38. Anal.
43.28, 65.67, 71.17, 71.63, 71.93, 72.70, 73.91, 75.78, 76.84, 108.47,
C17H29NO (375.42). Calcd (%): C, 54.39; H, 7.79; N, 3.73. Found
108.80, 176.29. MS: m/z calcd for C20H34NO (M+1) 416.23, found
8
8
(%): C, 54.20; H, 7.42; N, 4.02.
416.2.

6
590
D. E. Gremyachinskiy et al. / Tetrahedron Letters 44 (2003) 6587–6590
Acknowledgements
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P.; Pollini, G.; Zanirato, V. Tetrahedron: Asymmetry
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1
We thank Dr. Patrick R. Jones and Chang-Nan Chen
UOP) for their help with MS identification of synthe-
sized compounds.
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