Synthesis of (+)-1-deoxygalactonojirimycin

Article abstract of DOI:10.3987/com-03-s(p)12

A total synthesis of (+)-1-deoxygalactonojirimycin has been accomplished using stereoselective dihydroxylation and piperidine formation by catalytic hydrogenation.

Full text of DOI:10.3987/com-03-s(p)12

HETEROCYCLES, Vol. 62, 2004, pp. 333 - 341
Received, 25th June, 2003, Accepted, 28th August, 2003, Published online, 20th October, 2003
SYNTHESIS OF (+)-1-DEOXYGALACTONOJIRIMYCIN#
Sung-Jae Pyun, Kee-Young Lee, Chang-Young Oh, and Won-Hun Ham*
College of Pharmacy, SungKyunKwan University, Suwon, 440-746, Korea
whham@skku.edu
(# Dedicated to Professor Leo A. Paquette on the occasion of his 70th birthday.)
Abstract
-
A total synthesis of (+)-1-deoxygalactonojirimycin has been
accomplished using stereoselective dihydroxylation and piperidine formation by
catalytic hydrogenation.
A number of hydroxylated piperidines and pyrrolines occur in nature in plants and microorganisms.1
These natural products, which have been called “sugar-shaped” alkaloids from plants,2 are reversible,
competitive inhibitors of glycosidases. The purpose of these natural products is possibly to inhibit the
carbohydrate metabolism and consequently the growth of plant consuming pests. Since selective
glycosidase inhibitors have a large number of interesting potential applications including treatment of
AIDS,3 diabets,4 and anticancer agents,5 they have a considerable attention.
The “sugar-shaped” alkaloids (aza-sugars) closely resemble monosaccharides by being analogues of these
where the ring oxygen has been exchanged with a nitrogen atom. Thus nojirimycin (1)6 and 1-deoxy-
nojirimycin (2)7 are analogues of D-glucose and they are glucosidase inhibitors. Similarly natural
(+)-galactonojirimycin (3) and its reduction product (+)-1-deoxygalactonojirimycin (4) have been shown
to display strong inhibitory activity toward several β-galactosidases (Figure 1).8
In this report, we describe the stereoselective synthesis of (+)-1- deoxygalactonojirimycin by utilizing a
trans-oxazoline (8) as a chiral building block. Our retrosynthetic analysis is shown in Scheme 1.
Deoxy-azasugar (4) may be synthesized by hydrogenation and reduction of diol compound (11) which
would be prepared by dihydroxylation of α,β-unsaturated ester (10). And α,β-unsaturated ester (10) may

Figure 1
OH
OH
HO
R
OH
OH
HO
R
OH
OH
N
H
N
H
3. R = OH
4. R = H
1. R = OH
2. R = H
be synthesized by ring cleavage of trans-oxazoline (8) in Schotten-Baumann conditions, ozonolysis and
Horner-Wadsworth-Emmons reaction.
Scheme 1. Retrosynthetic Analysis
Hydrogenation
and Reduction
OH
OH OBz
HO
OH
OH
MeO2C
OTBS
OH NHCbz
N
H
11
4
Stereoselective
Dihydroxylation
TBSO
OBz
N
O
MeO2C
OTBS
NHCbz
10
D-serinol
Ph
8
In our previous report, 9 we showed that the palladium(0)-catalyzed oxazoline formation of homoallyl
benzamide coming from protected D-serinol might proceed with high stereoselectivity.
The synthesis of (+)-1-deoxygalactonojirimycin (4) began with D-N-benzoyl serinol (5) as shown in
Scheme 2. Oxidation of alcohol (5) with Dess-Martin periodinane gave the corresponding aldehyde
o
without racemization,10 which was reacted with vinylmagnesium bromide in THF at 0 C to afford the
corresponding allyl alcohol (6) as the ca. 1.1 : 1 mixture of syn/anti isomer (1H NMR analysis) in 75%
yield.11 Acetylation of the hydoxyl group yielded the secondary allylic acetate (7). The standard oxazoline
ring formation reaction (Pd(PPh3)4, K2CO3, in MeCN) of secondary allylic acetate (7) gave the desired
trans-oxazoline (8) in good yield (75%) as a single isomer.

Scheme 2
OH
a, b
TBSO
OH
NHBz
TBSO
NHBz
6
5
OAc
c
d
TBSO
8
NHBz
7
o
Reagents and conditions; a) Dess-Martin reagent, CH2Cl2, rt.; b) Vinylmagnesium bromide, THF, 0 C,
75% for two steps; c) Ac2O, Pyr, DMAP, CH2Cl2, rt, 99%; d) Pd(Ph3P)4,
K2CO3, MeCN, 55 oC, 75%
The trans-oxazoline (8) was treated with benzyl chloroformate in the presence of aqueous sodium
bicarbonate (Schotten-Baumann conditions),12 affording the carbamate (9) in 86% yield which was
converted into the α,β-unsaturated methyl ester (10) in 87% yield in two steps via ozonolysis and
subsequent Horner-Wadsworth-Emmons reaction. The dihydroxylation13 of 10 using a catalytic amount
of osmium tetroxide with 1.5 equiv. of N-methylmorpholine N-oxide as reoxidant (OsO4/NMO) in
CH2Cl2 afforded anti-diastereomer (11) in 80 % yield (> 20 : 1 1H NMR analysis). Hydrogenolysis of 11
with 10% Pd(OH)2 in AcOH/MeOH (1 : 10) was performed under 70 psi H2 at ambient temperature.
Under this condition, we achieved the cyclization of 11 in 62% yield. Reduction of 12 using
borane-methyl sulfide complex and deprotection with 6N hydrochlroric acid led to the formation of
13
(+)-1-deoxygalactonojirimycin (4) in 68% yield. The optical rotation and spectral data (1H NMR, C
NMR and HRMS spectrometry) of synthetic 4 were consistent with the reported values (Scheme 3).14
In summary, we report a new asymmetric synthetic method for the (+)-1-deoxygalactonojirimycin from
trans-oxazoline (8), which was achieved in 25% yield over 8 steps. The key features in this strategy are
the diastereoselective oxazoline formation reaction catalyzed by palladium(0), stereoselective
dihydroxylation and piperidine formation by catalytic hydrogenation.
EXPERIMENTAL
(-)-N-[(R)-2-Hydroxy-1-(tert-butyldimethylsilanyloxymethyl)but-3-enyl]benzamide (6).

Scheme 3
OBz
OBz
d
b, c
a
MeO2C
OTBS
OTBS
8
CbzHN
10
CbzHN
9
OH
OH
OH OBz
f, g, h
HO
OH
OH
e
HO
O
OBz
OTBS
MeO2C
OTBS
N
H
N
H
OH NHCbz
4
11
12
Reagents and conditions; a) CbzCl,NaHCO3, CH2Cl2/H2O, rt, 85%; b) O3 , MeOH, -78oC; c)
(MeO)2POCH2CO2Me, LiCl, iPr2NEt, MeCN, 86% for two steps; d) OsO4,
NMO, MC, 80% ( > 20 : 1); e) Pd(OH)2, H2, MeOH/AcOH (10 : 1), 62%;
f) BMS then NaOH, H2O2, THF, reflux; g) 6N HCl; h) DOWEX-50, 68%
for three steps
To a stirred solution of 5 (7.75 g, 25.05 mmol) in 50 mL of CH2Cl2 at 0 °C under argon was added
Dess-Martin periodinane (15.8 g, 37.58 mmol), and stirring was allowed to continue for 2 h. The reaction
mixture was diluted with Et2O (50 mL) followed by washing with saturated aqueous NaHCO3 solution
(50 mL × 2), brine (50 mL × 2), dried with MgSO4, and evaporated in vacuo. The crude aldehyde was
immediately employed in the next step without further purification. To a stirred solution of crude
aldehyde in THF (70 mL) at 0 °C, added with a double-tipped needle to a rt solution (125 mL, 1.0 M, 125
mmol) of vinylmagnesium bromide in THF. After being stirred for 1 h, the reaction mixture was washed
with saturated aqueous NH4Cl (100 mL × 2), brine (100 mL × 2), dried with MgSO4, and evaporated in
vacuo. Purification by silica gel chromatography (ethyl acetate/hexane = 1/10) gave 6 (6.54 g, 75%);
1
colorless oil; [α]24 -8.20 ° (c 1.0, CHCl3); IR (neat) 3427, 2930, 2857, 1643 cm-1; H NMR (500 MHz,
D
CDCl3) δ 0.058 (s, 3H), 0.096 (s, 3H), 0.91 (s, 9H), 3.62 (s, 1H), 3.99 - 4.01 (dd, J = 2.5 and 4.0 Hz, 2H),
4.16 (m, J = 2.5, 4.0 and 7.5 Hz, 1H), 4.64 (m, 1H), 5.21 (dt, J = 1.5 and 11.0 Hz, 1H), 5.39 (dt, J = 1.5
and 15.5 Hz, 1H), 5.88 (ddd, J = 6.0, 11.0 and 15.5 Hz, 1H), 6.79 (d, J = 7.5 Hz, 1H), 7.43 - 7.52 (m, 3H),
13
7.76 - 7.78 (m, 2H); C NMR (125 MHz, CDCl3) δ –5.33, 18.37, 26.04, 53.74, 65.36, 73.83, 116.47,
127.15, 128.86, 131.84, 134.60, 137.54, 167.91; HRMS (EI, 70eV) calcd for C18H29NO3Si 335.1917,
found 335.1917.

(-)-N-((1R, 2R)-2-Acetoxy-1-(tert-butyldimethylsilanyloxymethyl)-3-butenyl)benzamide (7).
To a stirred solution of 6 (3.5 g, 10.4 mmol) in CH2Cl2 (40 mL) were added acetic anhydride (1.1 mL,
14.2 mmol), pyridine (0.93 mL, 14.2 mmol), and stirring was allowed to continue for 12 h. The reaction
mixture was washed with 1N HCl (20 mL × 2), saturated aqueous NaHCO3 solution (20 mL × 2), brine
(20 mL × 2), dried with MgSO4, and evaporated in vacuo. Purification by silica gel chromatography
o
(ethyl acetate/hexane = 1/15) gave 7 (3.9 g, 99%); colorless oil; [α]25 -8.4 (c 1.0, CHCl3); IR (neat)
D
1
3322, 2931, 2857, 1745, 1646 cm-1; H NMR (500 MHz, CDCl3) δ 0.030 (s, 3H), 0.054 (s, 3H), 0.91 (s,
9H), 1.58 (s, 3H), 3.69 (dd, J = 3.0, 10.0 Hz, 1H), 3.82 (dd, J = 5.5, 10.0 Hz, 1H), 4.39 (m, 1H), 5.31 (dt,
J = 1.0, 11.0 Hz, 1H), 5.37 (dt, J = 1.0, 17.5 Hz, 1H), 5.67 (m, 1H), 5.88 (ddd, J = 6.5, 11.0, 17.5 Hz, 1H),
13
6.49 (d, J = 9.5 Hz, 1H), 7.43–7.52 (m, 3H), 7.74–7.75 (m, 2H); C NMR (125 MHz, CDCl3) δ -5.35,
18.42, 21.34, 26.03, 53.55, 62.00, 73.86, 119.41, 127.07, 128.93, 131.85, 133.71, 134.61, 167.25, 170.63;
HRMS (EI, 70 eV) calcd for C20H31NO4Si 377.2022, found 377.2027.
(4R, trans)-4,5-Dihydro-4-(tert-butyldimethylsilanyloxymethyl)-2-phenyloxazoline (8).
To a stirred solution of secondary allylic acetate (7) (4.0 g, 10.6 mmol) and K2CO3 (4.4 g, 31.78 mmol) in
MeCN (50 mL) was added Pd(PPh3)4 (61.2 mg, 0.53 mmol) under N2. The resulting mixture was heated
under reflux for 24 h, whereupon it was allowed to cool rt and was filtered through a pad of silica, which
was then evaporated under reduced pressure to give crude product. Purification by silica gel
o
chromatography (ethyl acetate/hexane = 1/15) gave 8 (2.52 g, 75%); colorless oil; [α]25 +3.66 (c 1.0,
D
1
CHCl3); IR (neat) 2930, 2857, 1650 cm-1; H NMR (500 MHz, CDCl3) δ 0.038 (s. 3H), 0.075 (s, 3H),
0.86 (s, 9H), 3.69 (dd, J = 7.0, 10.0 Hz, 1H), 3.94 (dd, J = 4.0, 10.0 Hz, 1H), 4.06 (ddd, J = 4.0, 5.5, 7.0
Hz, 1H), 5.02 (dd, J = 5.5, 6.5 Hz, 1H), 5.21 (dt, J = 1.5, 10.5 Hz, 1H), 5.36–5.40 (dt, J = 1.5, 17.0 Hz,
1H), 5.96 (ddd, J = 6.5, 10.5, 17.0 Hz, 1H), 7.39–7.48 (m, 3H), 7.95–7.97 (m, 2H); 13C NMR (125 MHz,
CDCl3) δ -5.08, 26.04, 64.95, 74.33, 83.31, 116.62, 128.02, 128.54, 131.59, 137.00, 164.11; HRMS m/e
calcd for C18H27NO2Si (M+1) 318.1889, found 318.1902.
1(R)-[2-(tert-Butyldimethylsiloxy)-1(R)-[[N-(phenylmethoxy)carbonyl]amino]ethyl]prop-2-enyl
benzoate (9).
To a solution of oxazoline (8) (3.32 g, 10.47 mmol) in CH2Cl2 (20 mL) was added a solution of NaHCO3
(3.52g, 41.90 mmol) in water (20 mL), and the mixture was cooled in an ice bath. To this solution was
added dropwise a solution of benzyl chloroformate (3.0 mL, 21.01 mmol). The mixture was stirred at rt
for 4 h. The organic phase was separated, and the aqueous phase was extracted with CH2Cl2 (2 × 20 mL).
The combined organic phase was washed with water, dried (MgSO4), and concentrated in vacuo.
Purification by silica gel chromatography (ethyl acetate/hexane = 1/4) gave 9 (4.18g, 85 %) as a colorless

o
1
oil; [α]23 +4.2 (c 1.0, CH2Cl2); IR (neat) : 3316, 3012, 2941, 1720, 1615 cm-1; H NMR (500 MHz,
D
CDCl3) : δ 0.03 (3H, s) 0.06 (3H, s), 0.90 ( 9H, s), 3.67 (1H, dd, J = 10, 5.5 Hz), 3.80 (1H, dd, J = 10, 3.5
Hz), 4.06 (1H, m), 5.04 (2H, s), 5.14 (1H, d, J = 10.5 Hz), 5.31 (1H, d, J = 10.5 Hz), 5.42 (1H, d, J = 17
Hz), 5.73 (1H, m), 5.92 (1H, m), 7.25 (5H, m), 7.43 (2H, m), 7.56 (1H, m), 8.04 (2H, m). 13C NMR (125
MHz, CDCl3) : δ -4.88, 18.91, 26.53, 55.71, 62.81, 67.54, 74.80, 119.94, 128.76, 128.84, 129.13, 129.18,
130.42, 130.74, 133.80, 134.15, 137.03, 156.90, 166.26; HRMS calcd for C26H35NO5Si (M+1) 470.2363,
Found 470.2354.
Methyl 4(R)-benzoxy-6-(tert -butyldimethylsiloxy)-5(R)-[[N-(phenylmethoxy)carbonyl]amino]hex-
2(E)-enoate (10).
o
Compound (9) (2.0 g, 4.26 mmol) was dissolved in dry methanol (50 mL) and cooled to –78 C. Pass
ozonied oxygen until the reaction is complete. The reaction mixture was evaporated under reduced
pressure. The crude aldehyde was immediately employed in the next step without further purification.
To a stirred solution of LiCl (217 mg, 5.11 mmol) in MeCN (80 mL) were added trimethylphosphono-
acetate (0.81 mL, 5.11 mmol) and iPr2NEt (0.89 mL, 5.11 mmol) and stirring was allowed to continue for
1 h. To this solution was added dropwise a solution of crude aldehyde (4.3 mmol) in MeCN (20 mL) and
the reaction mixture was stirred for 3 h. The reaction mixture was poured into H2O (30 mL), extracted
with EtOAc (20 mL × 2). The organic extract was washed with brine (20 mL), dried with MgSO4, and
evaporated in vacuo. Purification by silica gel chromatography (ethyl acetate/hexane = 1/2) gave
α,β-unsaturated ester (10) (1.95 g, 87 % for 2 steps) as a colorless oil; [α]23D +18.5 o (c 0.7, CH2Cl2); IR
(neat) : 3348, 3018, 2950, 1721, 1603, 1100 cm-1; 1H NMR (500 MHz, CDCl3) : δ 0.03 (6H, s), 0.87 (9H,
s), 3.66 (1H, dd, J = 10, 5.5 Hz), 3.74 (3H, s), 3.82(1H, dd, J = 10, 3 Hz), 5.06 (2H, s), 5.17 (1H, d, J = 10
Hz), 5.91 (1H, m), 6.07 (1H, d, J = 16 Hz), 7.01 (1H, dd, J = 16, 5.5 Hz), 7.28 (5H, m), 7.45 (2H, m),
13
7.58 (1H, m), 8.04 (2H, m); H NMR (125 MHz, CDCl3) : δ -4.95, -4.87, 14.91, 18.87, 21.75, 26.49,
52.44, 55.44, 62.64, 67.74, 72.65, 123.91, 128.64, 128.83, 128.91, 129.23, 129.26, 129.74, 130.06, 130.38,
130.48, 134.16, 136.84, 143.28, 156.67, 165.86, 166.67; HRMS calcd for C28H37NO7Si (M+1) 528.2418,
Found 528.2423.
(2R,3R,4S,6R)-4-Benzoxy-6-(tert -butyldimethylsiloxy)-5-[[N-(phenylmethoxy)carbonyl]amino]hexa-
noic Acid Methyl Ester 2,3,4,6-Tetrol (11)
To a stirred solution of 10 (500 mg, 0.95 mmol) in CH2Cl2 (20 mL) were added a N-methylmorpholine
N-oxide (166.5 mg, 1.43 mmol) and the solution of 4 wt. % OsO4/water (0.12 mL, 0.019 mmol, 2 mol %)
and the reaction was allowed to stir for 12 h, at which time all staring material had been consumed as
judged by TLC. The reaction mixture was poured into a solution of 15% Na2SO3 (50 mL), extracted with

CH2Cl2 (20 mL × 2). The organic extract was washed with brine (20 mL), dried with MgSO4, and
evaporated in vacuo. Purification by silica gel chromatography (ethyl acetate/hexane = 1/2) gave 11 (426
mg, 80 %, > 20 : 1) as a colorless oil; IR (neat) 3435, 2954, 2857, 1728, 1602, 1509, 113 cm-1; 1H NMR
(500 MHz, CDCl3) : δ -0.10 (6H, s), 0.86 (9H, s), 3.79 (3H, s), 3.80 (1H, d, J = 5 Hz), 4.13 (1H, m), 4.17
(1H, d, J = 6 Hz), 4.30 (1H, m), 4.37 (1H, d, J = 6 Hz), 5.19(2H, m), 5.38 (1H, d, J = 9.5 Hz), 5.55 (1H,
13
dd, J = 9 Hz, 1.5 Hz), 7.37 (5H, m), 7.43 (2H, m), 7.56 (1H, m), 8.03 (2H, m); C NMR (125 MHz,
CDCl3) : δ -4.98, 14.89, 18.84, 21.74, 26.44, 52.75, 54.40, 61.10, 64.04, 68.21, 71.21, 73.14, 128.74,
128.86, 129.06, 129.17, 129.31, 130.15, 130.55, 130.63, 130.74, 134.13, 136.71, 158.43, 165.92, 173.81;
HRMS calcd for C28H39NO9Si (M+1) 562.2472, Found 562.2473.
(3R, 4R, 5S, 6R)-5-Benzoxy-6-(tert-butyldimethylsilyloxymethyl)-3,4-dihydroxypiperidin-2-one (12)
To a solution of 11 (300 mg, 0.53 mmol) in 20 mL of 1:9 AcOH/MeOH were added 300 mg 10%
Pd(OH)2 and the reaction mixture was vigorously shaken under 70 psi H2 for 10 h at rt. The mixture was
then filtered and concentrated in vacuo. Purification by column chromatography (ethyl acetate/hexane =
4/1) over silica gel gave lactam (12) (131 mg, 62%) as a white solid; mp 72-73 oC; [α]23D +69.79 o (c 0.95,
CH2Cl2); IR (KBr) : 3392, 2931, 2857, 1726, 1671, 1468, 1268, 1110 cm-1;1H NMR (500 MHz, CDCl3) :
δ 0.00 (6H, s), 0.85 (9H, s), 3.52 (1H, m), 3.77 (2H, m), 4.17 (1H, dd, J = 10, 2 Hz), 4.44 (1H, d, J = 10
Hz), 5.83 (1H, s), 6.40 (1H, s), 7.46 (2H, m), 7.59 (1H, m), 8.01 (2H, m); 13C NMR (125 MHz, CDCl3) :
δ –4.84, 14.88, 18.80, 21.74, 26.45, 55.61, 63.30, 69.93, 70.84, 72.19, 129.26, 129.78, 130.59, 134.23,
166.57, 172.96; HRMS calcd for C19H29NO6Si (M+1) 396.1842, Found 396.1842.
(+)-1-Deoxygalactonojirimycin (4).
Borane-methyl sulfide complex (0.175 mL of a 10.1M solution in THF, 1.77 mmol) was added to a
cooled (0 °C) solution of the lactam (12) (100 mg, 0.25 mmol) in THF (5 mL). After 30 min, the solution
was warmed to rt. After another 2 h, the reaction was quenched by the slow addition of 3N NaOH and
30% H2O2 and heated at reflux for 1 h. After cooling to rt, to this solution was added excess 6N HCl (5
mL) and stirred for 3 h and the mixture concentrated in vacuo, and the residue was purified by using
ion-exchange chromatography (Dowex-50, H+) eluting with 3% NH4OH. Subsequent evaporation of
water in vacuo below 40 °C afforded a colorless syrup, which was dissolved in a small amount of
methanol and then precipitated by addition of acetone to give a hygroscopic, amorphous solid of
o
o
(+)-1-deoxygalactonojirimycin (4) (28 mg, 68%); [α]25D +52.5 (c 1.0. H2O) [lit.,13 [α]23D +52.8 (c 1.0.
H2O)]; IR(neat) 3448 cm-1 ; 1H NMR (500 MHz, D2O) : δ 2.41 (1H, dd, J = 12.5, 11.0 Hz), 2.77 (1H, dd,
J = 12.5, 6.5 Hz), 3.16 (1H, dd, J = 12.5, 5.5 Hz), 3.51(1H, dd, J = 9.7, 3.0 Hz), 3.65 (1H, dd, J = 11, 6.5
Hz), 3.7 (1H, dd, J = 11, 6.5 Hz), 3.77 (1H, dt, J = 11, 5.5 Hz), 4.03 (1H, dd, J = 3.2, 1.5 Hz); 13C NMR

(125 MHz, D2O with CH3CN as internal standard) δ 49.70, 59.43, 62.04, 68.83, 69.91, 75.70; HRMS
calcd for C6H13NO4 (M+1) 164.0923, Found 164.0924
ACKNOWLEDGEMENTS
This work was supported by grant No. R01-2001-000-00214-0 from Korea Science & Engineering
Foundation.
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