Synthesis of aza- and thia-spiroheterocycles and attempted synthesis of spiro sulfonium compounds related to salacinol

Article abstract of DOI:10.1016/j.carres.2007.07.003

The synthesis of aza- and thia-spiroheterocycles and the attempted synthesis of spiro sulfonium compounds related to salacinol are described. The binding of the nanomolar inhibitor swainsonine to Drosophila Golgi α-mannosidase II (dGMII) involves a large

Full text of DOI:10.1016/j.carres.2007.07.003

Carbohydrate Research 342 (2007) 2163–2172
Synthesis of aza- and thia-spiroheterocycles and attempted
synthesis of spiro sulfonium compounds related to salacinol
Wang Chen and B. Mario Pinto*
Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6
Received 9 June 2007; received in revised form 1 July 2007; accepted 3 July 2007
Available online 13 July 2007
Abstract—The synthesis of aza- and thia-spiroheterocycles and the attempted synthesis of spiro sulfonium compounds related to
salacinol are described. The binding of the nanomolar inhibitor swainsonine to Drosophila Golgi a-mannosidase II (dGMII)
involves a large contribution of interactions between the six-membered ring of the inhibitor and the hydrophobic pocket within
the enzyme active site. Salacinol, a naturally occurring sulfonium ion, is one of the active principles in the aqueous extracts of Sal-
acia reticulata that are traditionally used in Sri Lanka and India for the treatment of diabetes. Spiro aza- and thia-heterocycles and a
spiro analogue of salacinol were designed with the expectation that the hydrocarbon portions would make hydrophobic contribu-
tions to binding. The former sets of compounds were synthesized successfully but the salacinol analogue proved to be elusive. The
stereochemistry of the final compounds was determined by means of 1D-NOESY experiments. The aza- and thia-heterocycles were
not effective inhibitors of Golgi a-mannosidase II or human maltase glucoamylase.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Glycosidase inhibitors; Salacinol; Aza- and thia-spiroheterocycles; Curtius rearrangement; Enolate of a-thio ketone; Enolate of a-amino
ketone
1. Introduction
for the treatment of diabetes.6 Our group has reported
the syntheses of compounds 37 and 48 (Fig. 1) related
to salacinol that contain a carboxylate inner salt and
heteroanalogues of salacinol containing nitrogen9 or
selenium10 instead of sulfur, namely ghavamiol 5 and
blintol 6, respectively. Compounds 3, 4, and 6 inhibit
recombinant human maltase glucoamylase (MGA),11
one of the key intestinal enzymes involved in the break-
down of glucose oligosaccharides in the small intestine.
We reasoned that the interaction of a permanent posi-
tive charge with active-site carboxylate residues would
make a dominant contribution to the interaction energy.
In addition, compounds 1, 3, 5, and 6 were found to
inhibit Drosophila Golgi a-mannosidase II (dGMII), a
key enzyme involved in N-glycan processing and thus
a target in the development of anti-cancer therapies,
with IC50 values in the low mM range.7,12 The structure
of dGMII in complex with the inhibitor swainsonine 7
(IC50 20 nM, Figs. 2 and 3) has been published,13
although the reason for the potency of swainsonine
has not been clearly determined. The binding of the
Glycosidases belong to a group of hydrolytic enzymes
that are involved in a variety of biologically widespread
process. Their inhibition can have profound effects on
quality control, maturation, transport, and secretion of
glycoproteins and can alter cell–cell or cell–virus recog-
nition processes.1 The transition-state structure in the
enzyme-mediated hydrolysis of glycosides is believed
to be the oxacarbenium ion with a distorted conforma-
tion. Thus, mimicking this distorted, positively charged
species is one factor that could lead to a strong inhibitor
of glycosidase enzymes.2
The a-glucosidase inhibitors salacinol 1 and kotalanol
2 (Fig. 1) have been isolated from Salacia reticulata
WIGHT,3,4 and S. oblonga and S. chinensis,5 tradition-
ally used in the Ayurvedic system of India and Sri Lanka
*
Corresponding author. Tel.: +1 604 291 4152; fax: +1 604 291
4860; e-mail: bpinto@sfu.ca
0008-6215/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2007.07.003

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W. Chen, B. M. Pinto / Carbohydrate Research 342 (2007) 2163–2172
OH
OH
OH
OH
OH
OH
OH
S
OSO3 OH
S
OSO3
HO
HO
HO
OH
HO
1
2
OH OH
OH OH
CO2H
O
Cl
OH OH
NH
O
OH
S
HO
HO
HO
OH
HO
OH
3
4
OH
OH
Figure 3. Structure of swainsonine 7 bound in the active site of dGMII
(PDB 1HWW).
OH
OH
NH
OSO3
Se
OSO3
HO
HO
OH
HO
OH
HO
OH
NHCH2Ph
OH
5
6
HO
SMe
S
OSO3
Figure 1. Structures of salacinol 1, kotalanol 2, compounds 3 and 4,
ghavamiol 5, and blintol 6.
HO
HO
OH
HO
OH
9
10
OH
OH
H
Figure 4. Structures of the diastereomer of salacinol, 9, and N-benzyl
mannostatin 10.
HN
N
N
OH
OH
and the hydrophobic hydrocarbon moiety of swainso-
nine 7 that occupy the hydrophobic region of the active
site through which the hydrophilic C-5 hydroxyl groups
of salacinol analogues pass. The thiomethyl group,
which is critical for high affinity, is believed to make
important nonpolar interactions with aromatic rings in
the active site of dGMII.14 Accordingly, we also present
the attempted synthesis of spiro sulfonium compounds
11 and 12 (Fig. 6) related to salacinol but with more
nonpolar moieties than salacinol analogues themselves.
H
OH
HO
OH
OH
OH
7
8
Figure 2. Structures of swainsonine 7 and the aza-spiroheterocycle 8.
inhibitor involves a large contribution of hydrophobic
interactions with aromatic residues Trp95, Phe206, and
Tyr727. The plane of the six-membered ring is nearly
parallel to Phe206 and approximately at 90° to
Tyr727. Therefore, we now present the synthesis of the
aza-spiroheterocycle, 8 (Fig. 2), the hydrocarbon por-
tion of which is expected to interact with the hydropho-
bic pocket of Tyr727, Phe206, and Trp415.
2. Results and discussion
Overlay of compounds bound in the active site of
dGMII, obtained from X-ray crystallography, indicated
that the position of the head groups of 3, 5 and the
diastereomer of salacinol 9 is similar (Figs. 4 and 5).7
The positions of the nitrogen atoms and the positively
charged sulfur atom, which are designed to mimic the
positive charge on the oxacarbenium ion, are almost
identical. However, it is the thiomethyl group of a nano-
molar inhibitor N-benzyl mannostatin 10 (Figs. 4 and 5)
Paquette et al.15,16 have synthesized a number of 40-spi-
roalkylated nucleosides to impose conformational con-
straints that might have importance in modulation
of the sugar-phosphate DNA backbone, and ulti-
mately the secondary structure of DNA and base recog-
nition.17 Our synthesis takes advantage of the
stereochemistry of (R)-isopropylidene glyceraldehyde
and provides an alternative synthetic route to 40-spiro-
alkylated compounds.

W. Chen, B. M. Pinto / Carbohydrate Research 342 (2007) 2163–2172
2165
Figure 5. Overlay of compounds bound in the active site of dGMII. Compound 3 (cyan) is overlayed with A. Swainsonine 7 (pink, PDB 1HWW) B.
Ghavamiol 5 (magenta, PDB 1TQU) C. Salacinol Diastereomer 9 (gray, PDB 1TQT) or D. N-Benzyl mannostatin 10 (green, PDB 2F7P). Reprinted
with permission from Ref. 7.
OH
compound 19a, presumably formed by regioselective
tosylation of the primary alcohol, followed by a benzyl
sulfonium-ion intermediate. The hydroxyl groups of
19a were deprotected by Birch reduction to furnish the
thia-spiroheterocycle 20a. In a similar way, the spiro
compound 20b was synthesized (Scheme 1). Compound
19a was also transformed into its methoxymethyl deriv-
ative 19c for future use (Scheme 1).
The stereochemistry of 20a and 19b was confirmed on
the basis of NOE studies (Fig. 8). For example, the syn
nature of H-2a, H-3, H-4, and H-9a in 20a was made
evident by the strong correlations observed between
H-9a/H-4 and H-9a/H-3. A strong NOE with H-9a/H-
6 was also observed, indicating the syn relationship of
these two protons.
The synthesis of the aza-spiroheterocycle was exam-
ined next. Unlike the enolate of the a-thio ketone that
formed toward the a-substituent predominantly, the
enolates of the a-amino ketones 21 and 22 (Fig. 9) were
not readily accessible by conventional enolization tech-
niques.20 Thus, the b-ketoester 23 was employed as a
functional equivalent of 21 to react with the aldehyde
14 (Scheme 2). We reasoned that a Curtius rearrange-
ment21 would convert the carboxylate to an amine-
derived functional group. Thus, aldol condensation of
23 with 14 gave, after acylation of the hydroxyl group,
the four possible diastereomers 24a–d in a ratio of
30:6:5:1 (based on weight and NMR spectroscopic anal-
ysis). No other product was obtained. The major prod-
uct was presumably obtained through a six-membered
ring transition state and the stereochemical course of
OH OH
O
OH
OH
OH
O
OSO3
OH
S
S
HO
OH
HO
OH
11
12
Figure 6. Structures of the spiro sulfonium compounds 11 and 12.
2-Benzylsulfanylcyclopentanone 13 was prepared in
one step from the enolate of cyclopentanone and the
thiolating reagent S-benzyl 4-methylbenzenethiosulfo-
nate (Scheme 1). The lithium-catalyzed aldol reaction
of 13 with (R)-isopropylidene glyceraldehyde 1418 gave
two products 15a and 15b in a ratio of 3:1 that were sep-
arated by chromatography. No other diastereomer was
obtained. The reaction is believed to go through a six-
membered ring transition state with the enolate gener-
ated toward the a-substituent (Fig. 7). Both products
are predicted to arise by application of the Felkin-Anh
model for asymmetric induction, assuming the alkoxyl
group to be the ‘large’ group (Fig. 7).19 The major prod-
uct 15a was reduced selectively by NaBH4 to generate
16a, suggesting that the b-hydroxyl group helps to deli-
ver hydride from the si-face of the ketone. The hydroxyl
groups of compound 16a were benzylated and the iso-
propylidene protecting group was removed. Treatment
of compound 18a with tosyl chloride afforded the spiro

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W. Chen, B. M. Pinto / Carbohydrate Research 342 (2007) 2163–2172
O
O
OH
SBn
O
O
OH
SBn
O
LiBTMSA
LDA, THF
-78 ºC
THF, -78 ºC
SBn
+
+
O
O
O
H3CPh S SBn
O
O
O
O
O
15a,
22%
13,
14
15b,
60%
95%
NaBH4
MeOH
OH
SBn
OH
OBn
OBn
OBn
OBn
OBn
OBn
S
OH
SBn
NaH
SBn
AcOH
TsCl
O
O
OH
BnBr
MeOH
CH2Cl2
Pyridine
O
O
OH
16a, 85%
18a
52% for 3 three steps
17a
19a, 79%
º
Na/NH3
-78 C
OMOM
OMOM
OMOM
OH
OH
S
OH
S
MOMCl
N,N-diisopropylethylamine
20a, 61%
19c, 80%
OH
OBn
O
OBn
OBn
OH
S
OH
S
OH
SBn
SBn
TsCl
-78 ºC
Na/NH3
O
OH
CH2Cl2
Pyridine
O
OH
OBn
OH
15b
18b, 58%
19b, 77%
20b, 80%
Scheme 1.
O
O
SBn
O
O
O
O
O
O
O
O
Li
Li
BnO
O
O
H
Nu
H
H
H
Figure 7. Putative transition states for the aldol reaction.
b
a
H
H
b
a
H
H
OH
H
H
HO
OH
OH
OH
H
H
N
H
H
b
H
b
a
OBn
9
OH
H
8
S
4
H
H
b
6
9
2
5
2
S
4
8
H
H
3
4
7
3
7
2
H
5
6
H
H
3
7
a
H
H
9
8
6
a
H
H
H
H
H
OH
H
a
H
H
H
H
H
OBn
H
H
8
19b
20a
Figure 8. Observed NOE correlations for compounds 8, 19b, and 20a.
this aldol reaction corresponds to that predicted by the
Felkin-Anh model (Fig. 7).19 The optically pure 24d
was isolated by silica chromatography from the mixture
of its diastereomers 24a–c which was inseparable. The
ketone 24d was reduced stereoselectively to the alcohol
25 which was acylated subsequently. Compound 25
was converted to the benzyl carbamate 26 by a Curtius
rearrangement reaction. Deprotection of 26 and conver-

W. Chen, B. M. Pinto / Carbohydrate Research 342 (2007) 2163–2172
OLi
2167
19b, the stereochemistry at C-4, C-5, and C-6 in 8 was
confirmed on the basis of NOE studies (Fig. 8) by the
strong correlations observed between H-6/H-4 and H-
6/H-3. A strong NOE between H-3/H-2a indicated a
syn relationship of these two protons; a weak NOE
was also observed between H-3 and H-2b, as usually
observed in pyrrolidine derivatives.22
OLi
NPhth
N
CO2Et
22
21
Figure 9. Structures of enolates 21 and 22.
The synthesis of analogues of salacinol 1 was exam-
ined next. However, despite many attempts under a
variety of conditions, the coupling reactions of the com-
pounds 19a or 19c with the cyclic sulfate 30 or the epox-
ide 31 failed to yield the protected precursors of
analogues of salacinol 1, 32a/32b, or 33a/33b (Scheme
3).
sion of the resulting alcohol 27 to the tosylate 28 utilized
standard procedures. The amine in 28 was released and
subsequently treated, without purification, with DBU to
produce the desired spirocycles 29a and 29b as a 1:1
inseparable mixture that was subsequently deacylated
to furnish the target compound 8. As with compound
O
O
O
O
O
CO2Bn
CO2Bn
LDA, THF
-78 ºC
Pyridine
Ac2O
O
O
+
+
O
O
O
OBn
O
NaBH4/
MeOH
Pyridine
OAc
OAc
23
14
24a, 6%
24d, 36%
Ac2O
24b, 5%
24c, 1%
OAc
OAc
NHCbz
O
OAc
NHCbz
OH
OAc
NHCbz
OH
CO2Bn
O
a) H2, Pd/C
AcOH
H2O
TsCl
CH2Cl2
Pyridine
b) DPPA, Et N
O
O
OH
3
OTs
BnOH
OAc
25, 71%
OAc
26, 70%
OAc
27, 77%
OAc
28, 71%
H2, Pd/C
DBU, Benzene
OAc
H
N
OH
OH
H
N
OH
OAc
H
OH
N
NaOMe
+
OAc
OAc
OH
29a, 30%
29b, 30%
8, 72%
Scheme 2.
OH OH
O
OR1
O
O
O
O
OH
S
OBn
O
OR1
OR
S
2OR3
31
32a, R1=R2=Bn, R3=H
32b, R1=R2=R3=MOM
CH2Cl2, CF3CO2H
25 oC, 4 days
R2O
OR1
OR3
OH
o
HFIP,
75 C, 20 h
19a, R1=R2=Bn, R3=H
19c, R1=R2=R3=MOM
OH
O
O
O
O
O
OSO3
S
S
Ph
30
O
33a, R1=R2=Bn, R3=H
33b, R1=R2=R3=MOM
R2O
OR3
Scheme 3.

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W. Chen, B. M. Pinto / Carbohydrate Research 342 (2007) 2163–2172
Compounds 8, 20a, and 20b were tested for inhibition
(C-40), 67.86 (C-60), 63.73 (C-50), 57.71 (C-2), 36.18 (C-
5), 33.66 (SCH2PH), 29.24 (C-3), 26.61, 25.90 (2CH3),
18.26 (C-4). Anal. Calcd for C18H24O4S: C, 64.26; H,
7.19. Found: C, 64.58; H, 6.86.
of human maltase glucoamylase, a critical intestinal
enzyme involved in the breakdown of maltooligosaccha-
rides to glucose, as well as for inhibition of Golgi man-
nosidase II. These compounds did not show effective
inhibition of either enzyme, presumably because of poor
fit in the respective active sites.23
3.2. (1S,2R)-2-Benzylsulfanyl-2-[(R)-[(4R)-2,2-dimethyl-
1,3-dioxolan-4-yl]-hydroxymethyl]-cyclopentanol (16a)
To a solution of 15a (200 mg, 0.595 mmol) in dry MeOH
(20 mL) was added NaBH4 (10 mg, 2.0 equiv) slowly at
room temperature. When TLC showed the reaction to
be complete, the solvent was removed. The residue
was extracted with saturated NH4Cl and CH2Cl2. The
organic layer was concentrated to give 16a as a colorless
3. Experimental
3.1. (2R)-2-Benzylsulfanyl-2-[(R)-[(4R)-2,2-dimethyl-1,3-
dioxolan-4-yl]-hydroxymethyl]-cyclopentanone (15b) and
(2S)-2-benzylsulfanyl-2-[(R)-[(4R)-2,2-dimethyl-1,3-
dioxolan-4-yl]-hydroxymethyl]-cyclopentanone (15a)
1
oil (170 mg, 85%). [a]D ꢀ8 (c 0.02, acetone). H NMR
(CDCl3) d: 7.39–7.22 (5H, m, Ar), 4.29 (1H, dt,
J1,OH = 4.9 Hz, J1,5 = 8.1 Hz, H-1), 4.25 (1H, m, H-
40), 4.23 (1H, m, H-50a), 4.09 (1H, m, H-50b), 3.99,
3.92 (2H, d, JA,B = 12.1 Hz, 2SCH2Ph), 3.67 (1H, dd,
To a solution of diisopropylamine (0.74 mL) in dry
THF (13.4 mL) was added 2.0 M n-BuLi (2.6 mL) at
0 °C. After 10 min, the solution was cooled to ꢀ70 °C,
and 2-benzylsulfanylcyclopentanone (0.96 g, 4.65 mmol)
was added over 3 min. After the mixture had been stir-
red for 2 h at ꢀ70 °C, isopropylidene-D-glyceraldehyde
(0.604 g, 1.0 equiv) was slowly added and the mixture
was stirred for 20 min. The reaction was quenched by
the addition of a satd aq NaHCO3, the mixture was
extracted with ether, and the ether layer was concen-
trated. The crude product was purified by column chro-
matography (hexanes–EtOAc, 2:1) to afford 15a (0.93 g,
60%) and 15b (0.31 g, 22%) as colorless oils. Compound
J4 ;6 ¼ 6:4 Hz, J6 ;OH ¼ 5:9 Hz, H-60 CHOH), 1.98 (3H,
m, H-5a, H-5b, H-3a), 1.78 (2H, m, H-3b, H-4b), 1.63
(1H, m, H-4a), 1.42 (3H, s, CCH3), 1.37 (3H, s,
CCH3). 13C NMR (CDCl3) d: 137.13 (Cipso), 128.96–
127.12 (5CAr), 109.11 (C(CH3)2), 81.30 (C-1), 73.35 (C-
60), 76.66 (C-40), 67.49 (C-50), 64.24 (C-2), 33.52
(SCH2Ph), 32.02 (C-3), 30.66 (C-5), 26.65, 25.43
(2CH3), 19.39 (C-4). Anal. Calcd for C18H26O4S: C,
63.87; H, 7.74. Found: C, 63.58; H, 7.92.
0
0
0
1
15a [a]D ꢀ11 (c 0.02, acetone). H NMR (CDCl3) d:
3.3. (2R,3R)-3-Benzyloxy-3-[(1R,2S)-2-benzyloxy-1-
benzylsulfanylcyclopentyl]-propane-1,2-diol (18a) and
(2R,3R)-3-benzyloxy-3-[(1S,2R)-2-benzyloxy-1-benz-
ylsulfanylcyclopentyl]-propane-1,2-diol (18b)
0
0
7.34–7.22 (5H, m, Ar), 4.19 (1H, dd, J4 ;5 a ¼ 6:4 Hz,
J5 a;5 b ¼ 8:5 Hz, H-50a), 4.13 (1H, ddd, J4 ;5 b ¼ 5:0 Hz,
0
0
0
0
H-40), 3.97 (1H, dd, H-50b), 3.91 (1H, d, JA,B = 12.2 Hz,
SCH2Ph), 3.79 (1H, d, J4 ;6 ¼ 8:1 Hz, H-60 CHOH),
3.68 (1H, d, SCH2Ph), 2.58 (1H, dd, J4a,5a = 8.3 Hz,
J5a,5b = 18.7 Hz, H-5a), 2.35 (1H, dd, J4b,5b = 9.1 Hz,
H-5b), 2.67 (1H, m, H-3a), 2.06 (1H, m, H-4a), 1.95
(1H, m, H-4b), 1.80 (1H, dd, J3a,3b = 14.1 Hz,
J3a,4b = 6.8 Hz, H-3b), 1.34 (1H, s, CCH3), 1.34 (1H,
s, CCH3). 13C NMR (CDCl3) d: 211.87 (C@O), 137.25
(Cipso), 129.34–127.65 (5CAr), 109.98 (C(CH3)2), 75.75
(C-40), 73.35 (C-60), 68.46 (C-50), 60.40 (C-2), 36.89 (C-
5), 33.66 (SCH2Ph), 31.35 (C-3), 26.00, 25.53 (2CH3),
18.00 (C-4). Anal. Calcd for C18H24O4S: C, 64.26; H,
7.19. Found: C, 64.38; H, 7.09. Compound 15b [a]D
0
0
To a solution of 15a (200 mg, 0.595 mmol) in dry MeOH
(20 mL) was added NaBH4 (10 mg, 2.0 equiv) slowly at
room temperature. When TLC showed the reaction to
be complete, the solvent was removed. The residue
was extracted with saturated NH4Cl and CH2Cl2. The
organic layer was concentrated to give a colorless oil.
The resulting compound 16a was dissolved in dry
DMF (5 mL), NaH (55 mg, 2.0 equiv) was added slowly
at 0 °C, and the solution was stirred for 3 h. BnBr
(0.23 mL, 2.0 equiv) was added dropwise and the solu-
tion was stirred at room temperature for 2 h. The reac-
tion was quenched by the addition of MeOH and the
mixture was concentrated. The residue was extracted
with CH2Cl2 and brine, and the organic layer was con-
centrated to give a colorless oil. The resulting compound
17a was dissolved in 80% acetic acid and heated at reflux
for 1 h, after which the solvent was removed. The crude
product was purified by column chromatography (hex-
anes–EtOAc, 2:1) to afford 18a as a colorless oil
(0.147 g, 52%). Compound 18a [a]D ꢀ4 (c 0.04, acetone).
1H NMR (CDCl3) d: 7.41–7.26 (15H, m, Ar), 4.76
1
+53 (c 0.03, acetone). H NMR (CDCl3) d: 7.34–7.22
0
0
0
0
(5H, m, Ar), 4.56 (1H, ddd, J4 ;5 a ¼ 6:4 Hz, J4 ;5 b
¼
8:2 Hz, J4 ;6 ¼ 2:6 Hz, H-40), 4.45 (1H, d, H-60 CHOH),
3.90 (2H, m, H-50a, H-50b), 3.79 (1H, d, JA,B = 12.3 Hz,
SCH2Ph), 3.66 (1H, d, SCH2Ph), 2.63 (1H, dd,
J4a,5a = 8.3 Hz, J5a,5b = 18.8 Hz, H-5a), 2.41 (1H, m,
H-3a), 2.20 (1H, m, H-5b), 2.08 (1H, m, H-4a), 1.94
0
0
(1H, m, H-4b), 1.50 (1H, dd, J3a,3b = 13.4 Hz, J3a,4a
=
6.6 Hz, H-3b), 1.41 (1H, s, CCH3), 1.35 (1H, s,
CCH3). 13C NMR (CDCl3) d: 211.71 (C@O), 136.97
(Cipso), 129.37–127.54 (5CAr), 108.37 (C(CH3)2), 76.00
(1H, d, JA,B = 11.0 Hz, OCH2Ph), 4.58 (1H, d, JA,B
=

W. Chen, B. M. Pinto / Carbohydrate Research 342 (2007) 2163–2172
2169
11.6 Hz, OCH2Ph), 4.56 (1H, d, OCH2Ph), 4.48 (1H, d,
C22H26O3S: C, 71.32; H, 7.07. Found: C, 71.21; H,
7.22. Compound 19b was synthesized from 18b by a sim-
ilar procedure (77%). Compound 19b [a]D ꢀ97 (c 0.01,
acetone). 1H NMR (CDCl3) d: 7.42–7.22 (10H, m,
Ar), 4.63 (1H, d, JA,B = 12.3 Hz, OCH2Ph), 4.45 (1H,
d, JA,B = 11.5 Hz, OCH2Ph), 4.44 (1H, m, H-3), 4.43
(1H, d, OCH2Ph), 4.34 (1H, d, OCH2Ph), 3.76 (1H, d,
J3,4 = 4.1 Hz, H-4), 3.65 (1H, t, J6,7 = 8.0 Hz, H-6),
3.04 (1H, dd, J2a,2b = 11.6 Hz, J2a,3 = 5.3 Hz, H-2a),
2.88 (1H, dd, J2b,3 = 5.2 Hz, H-2b), 2.15 (1H, m, H-
9a), 1.94 (2H, m, H-7a, H-9b), 1.82 (1H, m, H-8a),
1.59 (1H, m, H-8b), 1.52 (1H, m, H-7b). 13C NMR
(CDCl3) d: 138.68, 137.79 (2Cipso), 128.80–127.97
(10CAr), 84.85 (C-4), 81.77 (C-6), 73.92 (OCH2Ph),
72.33 (OCH2Ph), 71.90 (C-3), 65.94 (C-5), 33.71 (C-
2), 33.25 (C-9), 28.55 (C-7), 19.70 (C-8). Anal. Calcd
for C22H26O3S: C, 71.32; H, 7.07. Found: C, 71.60; H,
7.30.
OCH2Ph), 4.29 (1H, t, J2 ;3 ¼ 7:7 Hz, H-20), 4.13 (1H,
m, H-2), 3.84 (1H, d, JA,B = 11.8 Hz, SCH2Ph), 3.81
(1H, dd, J1a,1b = 11.5 Hz, J1a,2 = 3.0 Hz, H-1a), 3.76
(1H, d, SCH2Ph), 3.77 (1H, dd, J1b,2 = 3.8 Hz, H-1b),
3.70 (1H, d, J2,3 = 7.9 Hz, H-3), 2.16–1.87 (5H, m, H-
30a, H-50a, H-30b, H-40a, H-50b), 1.60 (1H, m, H-40b).
13C NMR (CDCl3) d: 138.20, 138.10, 137.73 (3Cipso),
129.60–127.50 (15CAr), 81.82 (C-20), 80.06 (C-3), 75.58
(OCH2Ph), 73.73 (C-2), 72.00 (OCH2Ph), 64.13 (C-10),
62.82 (C-1), 33.09 (SCH2Ph), 33.01 (C-30), 29.50 (C-
50), 20.52 (C-40). Anal. Calcd for C29H34O4S: C, 72.77;
H, 7.16. Found: C, 72.59; H, 7.39. Compound 18b was
synthesized from 15b similarly in three steps (58%).
Compound 18b [a]D ꢀ3 (c 0.02, acetone). 1H NMR
(CDCl3) d: 7.40–7.20 (15H, m, Ar), 4.75 (1H, d,
JA,B = 11.1 Hz, OCH2Ph), 4.64 (1H, d, JA,B = 11.3 Hz,
OCH2Ph), 4.59 (1H, d, OCH2Ph), 4.39 (1H, d,
0
0
OCH2Ph), 4.26 (1H, m, H-2), 4.14 (1H, d, JA,B
=
11.7 Hz, SCH2Ph), 4.13 (1H, t, J2 ;3 ¼ 8:9 Hz, H-20),
3.91 (1H, d, SCH2Ph), 3.87 (2H, m, 2H-1), 3.73 (1H,
d, J2,3 = 7.9 Hz, H-3), 2.17 (2H, m, 2H-30), 2.07 (1H,
m, H-50a), 2.00 (1H, m, H-40a), 1.95 (1H, m, H-50b),
1.63 (1H, m, H-40b). 13C NMR (CDCl3) d: 138.60,
138.50, 137.45 (3Cipso), 129.49-127.20 (15CAr), 85.19
(C-20, C-3), 75.61 (OCH2Ph), 73.42 (C-2), 72.12
(OCH2Ph), 64.13 (C-10), 63.88 (C-1), 34.04 (SCH2Ph),
32.57 (C-50), 28.54 (C-30), 19.03 (C-40). Anal. Calcd for
C29H34O4S: C, 72.77; H, 7.16. Found: C, 72.43; H, 6.84.
3.5. (3R,4S,5R,6S)-1-Thia-spiro[4.4]nonane-3,4,6-triol
(20a) and (3R,4S,5S,6R)-1-thia-spiro[4.4]nonane-3,4,6-
triol (20b)
0
0
NH3 was condensed into a two-neck round bottom flask
at ꢀ78 °C, and lithium (1 cm wire) was added slowly. To
the resulting blue solution, 19a (190 mg, 0.51 mmol) in
dry ether (5 mL) was added dropwise. The mixture
was stirred for 0.5 h and then allowed to warm to room
temperature to allow NH3 to evaporate. At ꢀ78 °C, the
reaction was quenched by the addition of MeOH. The
mixture was concentrated and the crude product was
purified by column chromatography (CH2Cl2–MeOH,
10:1) to afford 20a as a colorless oil (61 mg, 61%). Com-
pound 20a [a]D ꢀ16 (c 0.06, MeOH). 1H NMR
(CD3OD) d: 4.25 (1H, ddd, H-3), 4.20 (1H, t,
J6,7 = 7.1 Hz, H-6), 3.86 (1H, d, J3,4 = 3.8 Hz, H-4),
2.97 (1H, dd, J2a,2b = 11.0 Hz, J2a,3 = 5.7 Hz, H-2a),
2.70 (1H, dd, J2b,3 = 4.4 Hz, H-2b), 2.02 (1H, m, H-
9a), 1.91 (1H, m, H-7a), 1.86 (1H, m, H-9b), 1.65 (1H,
m, H-8a), 1.59 (1H, m, H-7b), 1.56 (1H, m, H-8b). 13C
NMR (CD3OD) d: 78.84 (C-4), 74.44 (C-3), 72.42 (C-
6), 66.74 (C-5), 37.23 (C-9), 33.00 (C-2), 30.91 (C-7),
19.58 (C-8). Anal. Calcd for C8H14O3S: C, 50.50; H,
7.42. Found: C, 50.84; H, 7.56. Compound 20b was
obtained from 19b by a similar procedure (80%).
Compound 20b [a]D ꢀ77 (c 0.01, MeOH). 1H NMR
3.4. (3R,4S,5R,6S)-4,6-Bis-benzyloxy-1-thia-spiro[4.4]-
nonan-3-ol (19a) and (3R,4S,5S,6R)-4,6-bis-benzyloxy-1-
thia-spiro[4.4]nonan-3-ol (19b)
To a solution of 18a (0.9 g, 1.88 mmol) in CH2Cl2
(40 mL) and pyridine (2 mL) was added TsCl (0.36 g,
1.0 equiv). The mixture was stirred for 4 days. TLC
showed that the reaction was complete. The organic
solution was extracted with brine, the organic layer
was dried over Na2SO4, and concentrated. The crude
product was purified by column chromatography (hex-
anes–EtOAc, 4:1) to afford 19a as a colorless oil
(0.55 g, 79%). Compound 19a [a]D ꢀ4 (c 0.02, acetone).
1H NMR (CDCl3) d: 7.42–7.22 (10H, m, Ar), 4.81 (1H,
d, JA,B = 11.0 Hz, OCH2Ph), 4.71 (1H, d, JA,B
11.9 Hz, OCH2Ph), 4.55 (1H, d, OCH2Ph), 4.49 (1H,
m, H-3), 4.45 (1H, d, OCH2Ph), 4.16 (1H, dd, J6,7a
=
=
(CD3OD) d: 4.36 (1H, ddd, J2a,3 = 6.5 Hz, J2b,3 =
9.5 Hz, J6,7b = 7.4 Hz, H-6), 3.76 (1H, d, J3,4 = 3.9 Hz,
H-4), 3.04 (1H, dd, J2a,2b = 11.6 Hz, J2a,3 = 4.5 Hz, H-
2a), 2.84 (1H, d, H-2b), 2.10 (1H, m, H-9a), 1.96 (1H,
m, H-7a), 1.79 (1H, m, H-9b), 1.71 (1H, m, H-8a),
1.63 (1H, m, H-7b), 1.59 (1H, m, H-8b). 13C NMR
(CDCl3) d: 138.12, 137.13 (2Cipso), 128.45-126.93
(10CAr), 84.67 (C-4), 78.35 (C-6), 72.24 (OCH2Ph),
71.87 (OCH2Ph), 71.24 (C-3), 65.31 (C-5), 37.15 (C-9),
35.40 (C-2), 27.10 (C-7), 19.19 (C-8). Anal. Calcd for
7.6 Hz, J3,4 = 3.5 Hz, H-3), 3.74 (1H, t, J6,7 = 6.7 Hz,
H-6), 3.73 (1H, d, H-4), 2.87 (1H, dd, J2a,2b = 10.2 Hz,
H-2a), 2.83 (1H, dd, H-2b), 2.26 (1H, m, H-9a), 1.95
(1H, m, H-7a), 1.85 (1H, m, H-9b), 1.65 (1H, m, H-
8a), 1.56 (1H, m, H-8b), 1.52 (1H, m, H-7b). 13C
NMR (CD3OD) d: 78.22 (C-4), 76.95 (C-6), 74.95 (C-
3), 68.10 (C-5), 32.53 (C-9, C-2), 32.09 (C-7), 19.29 (C-
8). Anal. Calcd for C8H14O3S: C, 50.50; H, 7.42. Found:
C, 50.39; H, 7.29.

2170
W. Chen, B. M. Pinto / Carbohydrate Research 342 (2007) 2163–2172
3.6. (1R)-1-[(S)-Acetoxy-[(4R)-2,2-dimethyl-1,3-dioxo-
lan-4-yl]-methyl]-2-oxocyclopentane-carboxylic acid
benzyl ester (24d) and its diastereomers (24a–c)
H-2), 5.18, 5.08 (2H, d, JA,B = 12.2 Hz, OCH2Ph),
4.10 (1H, ddd, H-40), 3.88 (1H, dd, J4 ;5 a ¼ 6:39 Hz,
0
0
J5 a;5 b ¼ 8:20 Hz, H-50a), 3.69 (1H, dd, J4 ;5 b
¼
0
0
0
0
7:32 Hz, H-50b), 2.39 (1H, m, H-5a), 1.94 (2H, m, H-
5b, H-3a), 1.77 (1H, m, H-4a), 1.63 (1H, m, H-3b),
1.55 (1H, m, H-4b). 13C NMR (CDCl3) d: 172.37,
170.23, 169.87 (3C@O), 135.50 (Cipso), 128.80–128.49
(5CAr), 109.37 (C(CH3)2), 79.01 (C-2), 75.44 (C-40),
74.11 (C-60), 67.42 (CH2Ph), 66.55 (C-50), 59.43 (C-1),
32.49 (C-5), 30.26 (C-3), 26.32, 26.34 (C(CH3)2), 21.34
(C-4), 21.25 21.05 (2COCH3). Anal. Calcd for
C23H30O8: C, 63.58; H, 6.96. Found: C, 63.42; H, 7.04.
To a solution of diisopropylamine (0.68 mL) in dry THF
(12.4 mL) at 0 °C was added 2 M n-BuLi in pentane
(2.37 mL). After 10 min, the solution was cooled to
ꢀ78 °C, and 2-oxocyclopentanecarboxylic acid benzyl
ester (0.9 g, 4.13 mmol) was added over 3 min. After
the solution had been stirred for 2 h at ꢀ78 °C, 2,3-O-
isopropylidene-D-glyceraldehyde (0.536 g, 1.0 equiv)
was added. The mixture was stirred for 30 min and then
quenched by the addition of a satd aq NaHCO3. The
reaction mixture was extracted with ether twice. The
organic layer was concentrated, the residue was redis-
solved in CH2Cl2 (5 mL), and Ac2O (0.84 g, 2.0 equiv)
and pyridine (0.65 g, 2.0 equiv) were added to the solu-
tion, and the mixture was stirred overnight. The reaction
mixture was concentrated and the crude product was
purified by column chromatography (hexanes–EtOAc,
3:1) to afford a mixture of 24a, 24b and 24c (0.19 g,
6%, 5%, 1%) and 24d (0.57 g, 36%) as colorless oils.
Compound 24d [a]D ꢀ18 (c 0.03, MeOH). 1H NMR
(CDCl3) d: 7.38–7.28 (5H, m, Ar), 5.82 (1H, d,
3.8. [(1S,2R)-2-Acetoxy-1-[(S)-acetoxy-[(4R)-2,2-
dimethyl-1,3-dioxolan-4-yl]-methyl]cyclopentyl]-
carbamic acid benzyl ester (26)
A mixture of 25 (200 mg, 0.46 mmol) and Pd/C (10 mg)
in MeOH (10 mL) was stirred at room temperature
under an atmosphere of H2 for 10 h. The catalyst was
filtered and the solvent was removed. The residue was
dissolved in toluene (10 mL), and Et3N (48 mg,
1.0 equiv) was added, followed by the addition of DPPA
(308 mg, 1.0 equiv). After the mixture had been heated
at reflux for 2 h, BnOH (50 mg, 1.0 equiv) was added.
The mixture was heated at reflux for 12 h. The solvent
was removed and the crude product was purified by col-
umn chromatography (hexanes–EtOAc, 3:1) to afford 26
as a colorless oil (140 mg, 70%). Compound 26 [a]D +58
(c 0.01, acetone). 1H NMR (CDCl3) d: 7.38–7.30 (5H, m,
J4 ;6 ¼ 6:7 Hz, H-60 AcOCH), 5.20 (1H, d, JA,B
=
0
0
12.6 Hz, OCH2Ph), 5.04 (1H, d, OCH2Ph), 3.97 (2H,
m, H-40, H-50a), 3.86 (1H, m, H-50b), 2.74 (1H, m, H-
5a), 2.36 (1H, m, H-3a), 2.18 (2H, m, H-3b, H-5b),
2.02 (2H, m, 2H-4), 1.97 (3H, s, OCCH3), 1.25, 1.26
(6H, s, C(CH3)2). 13C NMR (CDCl3) d: 210.87
(CH2COC), 169.33, 166.74 (2CO2), 135.56 (Cipso),
128.77, 128.41, 127.95 (5CAr), 109.59 (C(CH3)2), 75.77
(C-40), 74.34 (C-60), 67.65 (OCH2Ph), 67.50 (C-50),
64.16 (C-1), 38.42 (C-3), 28.26 (C-5), 26.00, 25.59
(C(CH3)2), 20.89 (COCH3), 19.92 (C-4). Anal. Calcd
for C21H26O7: C, 64.60; H, 6.71. Found: C, 64.35; H,
6.75. Compound 24a–c Anal. Calcd for C21H26O7: C,
64.60; H, 6.71. Found: C, 64.29; H, 6.85.
0
0
Ar), 5.48 (1H, m, H-2), 5.40 (1H, d, J4 ;6 ¼ 6:0 Hz, H-
60), 5.06 (2H, s, OCH2Ph), 4.26 (1H, dt, J4 ;5
¼
0
0
6:47 Hz, H-40), 3.97 (1H, dd, J5 a;5 b ¼ 8:10 Hz, H-50a),
3.79 (1H, dd, H-50b), 2.18 (2H, m, H-3a, H-5a), 2.07
(7H, m, H-3b, 2COCH3), 1.78 (1H, m, H-4a), 1.68
(2H, m, H-5b, H-4b), 1.31, 1.30 (6H, s, C(CH3)2). 13C
NMR (CDCl3) d: 170.43, 169.91 (2OCOCH3), 154.89
(NHCO2Bn), 136.54 (Cipso), 128.75, 128.42, 128.33
(5CAr), 109.36 (C(CH3)2), 80.03 (C-1), 74.99 (C-40),
74.17 (C-60), 67.31 (OCH2Ph), 66.75 (C-2), 66.45 (C-
50), 33.64 (C-3), 31.89 (C-5), 26.39, 25.44 (C(CH3)2),
21.40, 21.17 (2COCH3), 20.31 (C-4). Anal. Calcd for
C23H31NO8: C, 61.46; H, 6.95, N, 3.12. Found: C,
61.13; H, 7.25, N, 3.33.
0
0
3.7. (1S,2R)-2-Acetoxy-1-[(S)-acetoxy-[(4R)-2,2-
dimethyl-1,3-dioxolan-4-yl]methyl]cyclopentane
carboxylic acid benzyl ester (25)
To a solution of 24d (0.67 g, 1.72 mmol) in MeOH
(50 mL) was added NaBH4 (130 mg, 2.0 equiv) slowly.
When TLC showed that the reduction was complete,
MeOH was removed. The residue was extracted with
CH2Cl2 and saturated NH4Cl. The organic layer was
concentrated. CH2Cl2 (10 mL) and Ac2O (0.35 g,
2.0 equiv) were added, and the resulting mixture was
stirred overnight. The mixture was concentrated and
the crude product was purified by column chromatogra-
phy (hexanes–EtOAc, 3:1) to afford 25 as a colorless oil
(0.53 g, 71%). Compound 25 [a]D +5 (c 0.06, MeOH).
1H NMR (CDCl3) d: 7.38–7.31 (5H, m, Ar), 5.53 (1H,
3.9. [(1S,2R)-2-Acetoxy-1-[(1S,2R)-1-acetoxy-2,3-
dihydroxypropyl]cyclopentyl]-carbamic acid benzyl
ester (27)
A mixture of 26 (1.7 g, 3.78 mmol) in 80% acetic acid
was heated at reflux for 10 min. The solution was con-
centrated under high vacuum. The crude product was
purified by column chromatography (hexanes–EtOAc,
1:1) to afford 27 as a colorless oil (1.2 g, 77%). Com-
1
pound 27 [a]D +41 (c 0.12, acetone). H NMR (CDCl3)
d, J4 ;6 ¼ 6:1 Hz, H-60), 5.45 (1H, t, J2,3 = 5.2 Hz,
d: 7.41–7.32 (5H, m, Ar), 5.48 (1H, d, J1 ;2 ¼ 9:5 Hz,
0
0
0
0

W. Chen, B. M. Pinto / Carbohydrate Research 342 (2007) 2163–2172
2171
H-10), 5.10, 5.07 (2H, d, JA,B = 12.3 Hz, OCH2Ph), 4.94
chromatography (hexanes–EtOAc, 1:1) to afford a 1:1
0
0
0
0
(1H, m, H-2), 3.67 (1H, ddd, J2 ;3 a ¼ 2:89 Hz, J2 ;3 b
¼
mixture of 29a and 29b as a white solid (27 mg, 60%).
Compound 29a H NMR (CD3OD) d: 5.09 (1H, ddd,
1
5:99 Hz, H-20), 3.54 (1H, dd, J3 a;3 b ¼ 11:6 Hz, H-30a),
3.43 (1H, dd, H-30b), 2.18 (1H, m, H-5a), 2.08 (6H, s,
2COCH3), 2.03 (1H, m, H-3a), 1.77 (3H, m, H-3b, H-
5b, H-4a), 1.70 (1H, m, H-4b). 13C NMR (CDCl3) d:
173.00, 171.01 (2OCOCH3), 156.20 (NHCO2Bn),
136.10 (Cipso), 128.75, 128.45, 128.13 (5CAr), 77.9 (C-
2), 74.10 (C-10), 70.50 (C-20), 68.30 (C-1), 67.50
(CH2Ph), 63.80 (C-30), 36.04 (C-5), 32.00 (C-3), 21.40,
21.37 (2COCH3), 19.95 (C-4). Anal. Calcd for
C20H27NO8: C, 58.67; H, 6.65, N, 3.42. Found: C,
58.85; H, 6.71, N, 3.46.
0
0
J2a,3 = 6.2 Hz, J2b,3 = 4.4 Hz, J3,4 = 5.3 Hz, H-3), 4.86
(1H, m, H-6), 4.2 (1H, d, H-4), 3.10 (1H, dd,
J2a,2b = 12.6 Hz, H-2a), 2.90 (1H, dd, H-2b), 2.20 (1H,
m, H-7a), 2.18 (1H, m, H-9a), 2.07, 2.05 (2COCH3),
1.73 (1H, m, H-8a), 1.72 (1H, m, H-7b), 1.65 (1H, m,
H-8b), 1.62 (1H, m, H-9b). 13C NMR (CD3OD) d:
171.32, 171.07 (2OCOCH3), 80.73 (C-6), 75.24 (C-3),
73.22 (C-5), 72.21 (C-4), 47.82 (C-2), 31.57 (C-7),
30.32 (C-9), 20.17 (C-8), 19.91, 19.73 (2COCH3). Com-
pound 29b 1H NMR (CD3OD) d: 5.10 (1H, d,
J3,4 = 5.1 Hz, H-4), 4.86 (1H, m, H-6), 4.30 (1H, ddd,
H-3), 3.08 (1H, dd, J2a,2b = 11.8 Hz, J2a,3 = 6.0 Hz, H-
2a), 2.84 (1H, dd, J2b,3 = 5.3 Hz, H-2b), 2.34 (1H, m,
H-9a), 2.12 (COCH3), 2.08 (1H, m, H-7a), 2.00
(COCH3) 1.73 (1H, m, H-8a), 1.65 (1H, m, H-8b),
1.64 (1H, m, H-7b), 1.5 (1H, m, H-9b). 13C NMR
(CD3OD) d: 171.28, 170.92 (2OCOCH3), 80.65 (C-6),
75.39 (C-4), 72.52 (C-5), 70.91 (C-3), 50.24 (C-2),
31.68 (C-7), 30.63 (C-9), 20.17 (C-8), 19.91, 19.67
(2COCH3). Anal. Calcd for C12H19NO5: C, 56.02; H,
7.44, N, 5.44. Found: C, 55.78; H, 7.65, N, 5.76.
3.10. [(1S,2R)-2-Acetoxy-1-[(1S,2R)-1-acetoxy-2-
hydroxy-3-(toluene-4-sulfonyloxy)propyl]cyclopentyl]-
carbamic acid benzyl ester (28)
To a solution of 27 (200 mg, 0.489 mmol) in pyridine–
CH2Cl2 (10 mL, 20:1) was added TsCl (94 mg, 1.0 equiv).
The mixture was stirred for 4 days. When TLC showed
the reaction to be complete, the mixture was extracted
with a saturated NH4Cl solution three times. The organ-
ic layer was concentrated and the crude product was
purified by column chromatography (hexanes–EtOAc,
1:1) to afford 28 as a colorless oil (190 mg, 71%). Com-
3.12. (3S,4R,5S,6R)-1-Aza-spiro[4.4]nonane-3,4,6-triol
(8)
1
pound 28 [a]D +21 (c 0.01, MeOH). H NMR (CDCl3)
d: 7.78 (2H, d, 2Ar), 7.35 (5H, m, Ar), 5.26 (1H, d,
J1 ;2 ¼ 9:0 Hz, H-10), 5.10, 5.06 (2H, d, JA,B = 12.1 Hz,
A mixture of 29a and 29b (25.7 mg, 0.1 mmol) was dis-
solved in dry MeOH (2 mL) and 1 M sodium methoxide
(2 mL) was added. The mixture was stirred for 1 h at
room temperature and the solvent was removed. The
residue was purified by column chromatography
(CH2Cl2–MeOH, 1:1) to afford 8 as a colorless oil
(13 mg, 72%). [a]D ꢀ4.5 (c 0.02, MeOH). 1H NMR
(CD3OD) d: 4.22 (1H, ddd, H-3), 4.12 (1H, d,
J3,4 = 5.2 Hz, H-4), 3.77 (1H, t, J6,7 = 5.2 Hz, H-6),
3.02 (1H, dd, J2a,2b = 11.9 Hz, J2a,3 = 6.2 Hz, H-2a),
2.77 (1H, dd, J2b,3 = 4.9 Hz, H-2b), 2.19 (1H, ddd,
J8a,9a = 7.2 Hz, J8b,9a = 9.4 Hz, J9a,9b = 13.5 Hz, H-9a),
2.04 (1H, m, H-7a), 1.75 (1H, m, H-8a), 1.63 (2H, m,
H-7b, H-8b), 1.49 (1H, ddd, J8a,9b = 5.0 Hz,
J8b,9b = 8.5 Hz, H-9b). 13C NMR (CD3OD) d: 77.98
(C-6), 74.67 (C-5), 72.78 (C-4), 72.34 (C-3), 50.12 (C-
2), 32.52 (C-7), 30.37 (C-9), 19.65 (C-8). HRMS Calcd
for C8H16NO3 (M+H): 174.1125. Found: 174.1120.
0
0
0
0
OCH2Ph), 4.78 (1H, m, H-1), 4.00 (1H, dd, J2 ;3 a
¼
2:8 Hz, J3 a;3 b ¼ 9:8 Hz, H-30a), 3.92 (1H, dd,
0
0
J2 ;3 b ¼ 5:34 Hz, H-30b), 3.89 (1H, ddd, H-20), 2.45
(3H, s, PhCH3), 2.15 (2H, m, H-3a, H-5a), 2.05, 2.08
(6H, s, 2COCH3), 1.78 (3H, m, H-3b, H-5b, H-4a),
1.65 (1H, m, H-4b). 13C NMR (CDCl3) d: 170.30,
0
0
170.11 (2OCOCH3), 156.45 (NHCO2Bn), 145.10 (Cipso
-
(SO3Ph)), 136.09 (Cipso(CH2Ph)), 132.78 (Cipso(PhCH3)),
130.01–128.27 (9CAr), 77.3 (C-2), 73.70 (C-10), 71.1 (C-
20), 68.74 (C-1), 68.7 (CH2Ph), 67.4 (C-30), 35.9 (C-3),
31.8 (C-5), 21.8 (PhCH3), 21.24, 21.00 (2COCH3),
19.23 (C-4). Anal. Calcd for C27H33NO10S: C, 57.54;
H, 5.90, N, 2.49. Found: C, 57.41; H, 6.07, N, 2.65.
3.11. (3S,4R,5R,6R)-Acetic acid 3-acetoxy-4-hydroxy-1-
aza-spiro[4.4]non-6-yl ester (29a) and (3S,4R,5S,6R)-
acetic acid 4-acetoxy-3-hydroxy-1-aza-spiro[4.4]non-6-yl
ester (29b)
3.13. 3,4,6-Tris-methoxymethoxy-1-thia-spiro[4.4]nonane
(19c)
A mixture of 28 (100 mg, 0.177 mmol) and Pd/C (10 mg)
in acetic acid (5 mL) was stirred under an atmosphere of
H2 for 10 h. When TLC showed the reaction to be
complete, the catalyst was filtered and the solvent was
removed under high vacuum. Benzene (10 mL) and
DBU (54 mg, 2.0 equiv) were added and the mixture
was heated at reflux for 3 h. The mixture was concen-
trated and the crude product was purified by column
To a solution of compound 20a (30 mg, 0.158 mmol)
and N,N-diisopropylethylamine (0.4 mL) in DMF
(1 mL) was added chloromethyl methyl ether (75 mg,
2.0 equiv) at room temperature. The mixture was stirred
for 18 h and the solvent was removed. The residue was
purified by column chromatography (hexanes–EtOAc,

2172
W. Chen, B. M. Pinto / Carbohydrate Research 342 (2007) 2163–2172
Tetrahedron Lett. 1997, 38, 8367–8370; (b) Yoshikawa,
M.; Morikawa, T.; Matsuda, H.; Tanabe, G.; Muraoka,
O. Bioorg. Med. Chem. 2002, 10, 1547–1554.
5:1) to afford 19c as a colorless oil (40 mg, 80%). Com-
pound 19c [a]D ꢀ18 (c 0.06, MeOH). 1H NMR (CDCl3)
d: 4.95 (1H, d, JA,B = 7.1 Hz, OCH2O), 4.79 (1H, d,
JA,B = 6.8 Hz, OCH2O), 4.70 (1H, d, OCH2O), 4.69
(1H, d, JA,B = 6.7 Hz, OCH2O), 4.65 (1H, d, OCH2O),
4.64 (1H, d, OCH2O), 4.35 (1H, ddd, J2a,3 = 7.2 Hz,
J2b,3 = 9.8 Hz, J3,4 = 2.8 Hz, H-3), 4.28 (1H, d, H-4),
3.43 (3H, s, CH3), 3.43 (3H, s, CH3), 3.38 (3H, s,
CH3), 2.98 (1H, dd, J2a,2b = 10.0 Hz, H-2a), 2.95 (1H,
dd, H-2b), 2.10 (1H, m, H-8a), 1.89 (3H, m, H-7a, H-
7b, H-9a), 1.80 (1H, m, H-8b), 1.68 (1H, m, H-9b).
13C NMR (CDCl3) d: 97.42, 96.12, 95.98 (3OCH2O),
82.09 (C-6), 81.93 (C-4), 80.46 (C-3), 64.91 (C-5),
56.70, 55.90, 55.79 (3CH3), 40.83 (C-8), 30.32 (C-2),
30.11 (C-7), 21.89 (C-9). HRMS Calcd for C14H26O6S:
322.1452. Found: 322.1442.
4. Yoshikawa, M.; Murakami, T.; Yashiro, K.; Matsuda, H.
Chem. Pharm. Bull. 1998, 46, 1339–1340.
5. Matsuda, H.; Murakami, T.; Yashiro, K.; Yamahara, J.;
Yoshikawa, M. Chem. Pharm. Bull. 1999, 47, 1725–
1729.
6. Matsuda, H.; Morikawa, T.; Yoshikawa, M. Pure Appl.
Chem. 2002, 74, 1301–1308.
7. Chen, W.; Kuntz, D. A.; Hamlet, T.; Sim, L.; Rose, D. R.;
Pinto, B. M. Bioorg. Med. Chem. 2006, 14, 8332–8340.
8. Chen, W.; Sim, L.; Rose, D. R.; Pinto, B. M. Carbohydr.
Res. 2007, 342, 1661–1667.
9. Ghavami, A.; Johnston, B. D.; Jensen, M. T.; Svensson,
B.; Pinto, B. M. J. Am. Chem. Soc. 2001, 123, 6268–6271.
10. Johnston, B. D.; Ghavami, A.; Jensen, M. T.; Svensson,
B.; Pinto, B. M. J. Am. Chem. Soc. 2002, 124, 8245–8250.
11. Rossi, E. J.; Sim, L.; Kuntz, D. A.; Hahn, D.; Johnston, B.
D.; Ghavami, A.; Szczepina, M. G.; Kumar, N. S.;
Sterchi, E. E.; Nichols, B. L.; Pinto, B. M.; Rose, D. R.
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Acknowledgments
12. Kuntz, D. A.; Ghavami, A.; Johnston, B. D.; Pinto, B. M.;
Rose, D. R. Tetrahedron: Asymmetry 2005, 16, 25–32.
13. Van den Elsen, J. M. H.; Kuntz, D. A.; Rose, D. R.
EMBO J. 2001, 20, 3008–3017.
14. Kawatkar, S. P.; Kuntz, D. A.; Woods, R. J.; Rose, D. R.;
Boons, G.-J. J. Am. Chem. Soc. 2006, 128, 8310–8319.
15. (a) Paquette, L. A.; Kahane, A. L.; Seekamp, C. K. J. Org.
Chem. 2004, 17, 5555–5562; (b) Paquette, L. A.; Owen, D.
R.; Bibart, R. T.; Seekamp, C. K. Org. Lett. 2001, 3, 4043–
4046.
We are grateful to Ravindranath Nasi and Blair D.
Johnston for helpful discussion and to the Natural Sci-
ences and Engineering Research Council of Canada
for financial support.
Supplementary data
16. (a) Paquette, L. A.; Fabris, F.; Gallou, F.; Dong, S.
J. Org. Chem. 2003, 68, 8625–8634; (b) Dong, S.; Paquette,
L. A. J. Org. Chem. 2005, 70, 1580–1596; (c) Paquette, L.
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Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.carres.
2007.07.003.
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