Biological evaluation of 3′-O-alkylated analogs of salacinol, the role of hydrophobic alkyl group at 3′ position in the side chain on the α-glucosidase inhibitory activity

Article abstract of DOI:10.1016/j.bmcl.2011.02.109

Four analogs with 3′-O-alkyl groups (9a: CH₃, 9b: C ₂H₅, 9c: C₁₃H₂₇ or 9d: CH ₂Ph) instead of the 3′-O-sulfate anion in salacinol (1), a naturally occurring potent α-glucosidase inhibitor, were synthesized by the coupling reaction of 1,4-dideoxy-1,4-epithio-d-arabinitols (18a and 18b) with appropriate epoxides (10a-10d). These analogs showed equal or considerably higher inhibitory activity against rat small intestinal α-glucosidases than the original sulfate (1), and one of them (9d) was found more potent than currently used α-glucosidase inhibitors as antidiabetics. Thus, introduction of a hydrophobic moiety at the C3′ position of this new class of inhibitor was found beneficial for onset of stronger inhibition against these enzymes.

Full text of DOI:10.1016/j.bmcl.2011.02.109

Bioorganic & Medicinal Chemistry Letters 21 (2011) 3159–3162
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Biological evaluation of 30-O-alkylated analogs of salacinol, the role
of hydrophobic alkyl group at 30 position in the side chain
on the a-glucosidase inhibitory activity
Genzoh Tanabe a, Tetsu Otani a, Wenying Cong a, Toshie Minematsu a, Kiyofumi Ninomiya b,
Masayuki Yoshikawa b,c, Osamu Muraoka a,
⇑
a School of Pharmacy, Kinki University, 3-4-1 Kowakae, Higashi-osaka, Osaka 577-8502, Japan
b Pharmaceutical Research and Technology Institute, Kinki University, 3-4-1 Kowakae, Higashi-osaka, Osaka 577-8502, Japan
c Kyoto Pharmaceutical University, 1 Shichono-cho, Misasagi, Yamashina-ku, Kyoto 607-8412, Japan
a r t i c l e i n f o
a b s t r a c t
Four analogs with 30-O-alkyl groups (9a: CH3, 9b: C2H5, 9c: C13H27 or 9d: CH2Ph) instead of the 30-O-sul-
Article history:
Received 2 November 2010
Revised 24 February 2011
Accepted 26 February 2011
Available online 11 March 2011
fate anion in salacinol (1), a naturally occurring potent
coupling reaction of 1,4-dideoxy-1,4-epithio- -arabinitols (18a and 18b) with appropriate epoxides
(10a–10d). These analogs showed equal or considerably higher inhibitory activity against rat small intes-
tinal -glucosidases than the original sulfate (1), and one of them (9d) was found more potent than cur-
rently used
a-glucosidase inhibitor, were synthesized by the
D
a
a
-glucosidase inhibitors as antidiabetics. Thus, introduction of a hydrophobic moiety at the
Keywords:
C30 position of this new class of inhibitor was found beneficial for onset of stronger inhibition against
a
-Glucosidase inhibitor
these enzymes.
30-O-Alkylated neosalacinol
Salacinol
Ó 2011 Elsevier Ltd. All rights reserved.
Neosalacinol
Thiosugar
Glycosidases are involved in several important biological pro-
cesses (e.g., digestion, the biosynthesis of glycoproteins, and the
lysosomal catabolism of glycoconjugates), thus glycosidase inhibi-
tors have many potential therapeutic applications and have been
implicated in several disease states,1 such as diabetes, cancers
and viral infections. Many naturally occurring and synthesized aza-
sugars, which are believed to carry a positive charge at physiolog-
ical pH and hence are postulated to bind in the active sites of
glucosidase enzymes, are effective inhibitors of various glycosi-
dases.1 These evidences indicated that a potent glucosidase inhib-
itor might include an atom that carries a permanent positive
charge at a suitable position that mimic the oxacarbenium ion-like
transition state of the enzyme-catalyzed reaction.1b
vealed to be as potent as those of voglibose and acarbose which
are widely used clinically these days.2 Since the discovery of 1, re-
lated sulfonium sulfates, kotalanol3 (2), ponkoranol4 (3) and
salaprinol4 (4) were subsequently isolated, and the stereostructure
of these sulfonium sulfates (2, 3, 4) were elucidated by total syn-
theses or other means.5 (Fig. 1)
Thereafter, their desulfonated versions, neosalacinol6 (5),
neokotalanol4,7 (6) neoponkoranol8 (7) and neosaraprinol8 (8)
were also isolated subsequently, and found as potent as their origi-
nal sulfonates. The mode of action of 1 was also proved to be com-
petitive inhibition against
rat intestinal -glucosidases, that is, maltase, sucrase, and isomalt-
ase were revealed as 0.31, 0.32, and 0.47
g/mL, respectively.2b Be-
cause of their intriguing structure and high -glucosidase
a-glucosidase, and Ki values of 1 against
a
l
In late 1990s0, salacinol (1) was isolated by the authors as one of
the physiologically active components of an ayurvedic medicinal
plant Salacia reticulata, which have traditionally been used for
the treatment of diabetes in Sri Lanka and south region of India.2
The structure of 1 was quite unique, bearing the permanent posi-
tive charge as the thiosugar sulfonium sulfate inner salt comprised
a
inhibitory activities, much attention has been focused on them,
and intensive structure–activity relationships (SAR) studies on this
new class of
a-glucosidase family have been reported, determi-
nants required for the activity being revealed to a certain ex-
tent.5b,9 By the recent intensive X-ray crystallographic studies on
N-terminal catalytic domain of maltase–glucoamylase (ntMGAM)
in complex with kotalanol (2) and neokotalanol (6),9f and also by
of 1-deoxy-4-thio-D
-arabinofranosyl cation and 30-sulfate anion as
shown in Figure 1. Its
a-glucosidase inhibitory activity was re-
an in silico docking studies of salacinol (1) with an a
-glucosidase,9g
it was reported that the 30-O-sulfate anion seemed to be con-
strained by hydrophobic residues of the enzymes, and made no
hydrogen bonding interactions with them.
⇑
Corresponding author. Tel.: +81 6 6721 2332; fax: +81 6 6721 2505.
E-mail address: muraoka@phar.kindai.ac.jp (O. Muraoka).
0960-894X/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2011.02.109

3160
G. Tanabe et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3159–3162
OH
OH
OH
3'S
OH OH OH
OH OH
3'
OH
3'
X-
5'
7'
OH
1'
4'
OH
2'
2'S
4'R
2'
4'
OH
S+ OR
OH
5
S+ OR
OH
S+ OR
S+
S+
OH
OH
OR
OR
HO
1
HO
HO
4
HO
HO
3
2
HO
OH
HO
HO
OH
HO
OH
HO
-
-
-
-
salacinol (1)
: R = SO3
: R = H
kotalanol (2)
3'-O
-alkylated neosalacinol (9)
R = CH3, C2H5, PhCH2, C13H27
X = BF4 or Cl
salaprinol (4)
: R = SO3
neosalaprinol (8) : R = H
: R = SO3
: R = H
ponkoranol (3)
: R = SO3
: R = H
neosalacinol (5)
neokotalanol (6)
neoponkoranol (7)
Figure 1. Sulfonium families as a new class of
a-glucosidase inhibitors.
In this Letter, with an expectation of increment of the hydro-
phobic interactions of the molecule at this hydrophobic residue
of the enzymes, four analogs (9a–9d) of salacinol (1), in which
the 30-O-sulfate moiety was replaced by OCH3, OC2H5, OC13H27 or
OCH2Ph groups, were synthesized and their inhibitory activities
were evaluated. Considerable enhancements of the inhibitory
activity have been observed as was anticipated for the synthesized
compounds.
OH
OH
OBn
OR
OBn
OR
iii
O
O
HO
HO
O
O
11
15
10
14
16
ii
iv
i
OBn
OH
OPMB
OBn
OBn
OR
O
O
O
O
Synthesis of 9 was carried out by applying the regioselective
ring-opening reaction of appropriate epoxides with a thiosugar.
Thus, epoxides 10a, 10b, and 10c were first prepared in the follow-
O
O
12
v
ing manner. 3,4-O-isopropylidene-
via four steps starting from
-isoascorbic acid,10 was subjected to
selective benzylation of the primary hydroxyl to give 1-O-benzyl-
3,4-O-isopropylidene-
-erythritol11 (12) and 2-O-benzyl-3,4-O-iso-
propylidene-
-erythritol12 (13) in 91% and 7% yields, respectively.
D-erythritol (11), easily obtained
vi
+
D
OH
OPMB
OBn
OPMB
OBn
10d
iv
O
HO
HO
D
OBn
O
D
13
17
Alkylation of the major alcohol 12 with CH3I, C2H5I or C13H27Br in
DMF in the presence of NaH, and subsequent deacetonization of
a : R = CH3, b : R = C2H5, c : R = C1 H27, d : R = PhCH2
the resulting
of hydrochloric acid gave 2-O-alkyl-1-O-benzyl-
D
-erythritol derivatives (14a, 14b, and 14c) by action
-erythritol (15a,
D
Scheme 1. Reagents and conditions: (i) Bu2SnO, toluene, reflux, then BnBr, CsF,
DMF, 60 °C; (ii) CH3I, C2H5I, or C13H27Br, NaH, DMF, 0 °C to rt; (iii) 0.5% aq HCl, EtOH,
reflux; (iv) Ph3P, DEAD, toluene, reflux; (v) PMBCl, NaH, DMF, 0 °C; (vi) AcOH/H2O
(2:1, v/v), rt.
15b, and 15c), respectively, in good yields. Glycols 15a, 15b, and
15c were then subjected to the Mitsunobu reaction by treatment
with DEAD and Ph3P in refluxing toluene to give the desired epox-
ides 10a, 10b, and 10c in 77%, 76%, and 81% yields, respectively.
Meanwhile, deacetonization of 2-O-benzyl-1-O-(p-methoxyben-
NMR spectra of 9a, 9b, 9c and 9d were similar with each other,
and the significant down field shift of signals due to the C03
methine carbon corresponded to the 30-O-alkylated neosalacinol-
type structure. The anti relationship between the side chain and
the hydroxymethyl moiety on C4 of 9a, 9b, 9c, and 9d was con-
firmed by means of nuclear Overhauser effect (NOE) experiments
as was shown in Scheme 2.
zyl)-3,4-O-isopropylidene-
by alkylation of minor alcohol 13 with PMBCl, in aqueous acetic
acid gave 2-O-benzyl-1-O-(p-methoxybenzyl)- -erythritol (17) in
87% yield. Epoxydation of 17 under the Mitsunobu conditions gave
the desired 1-O-p-methoxybenzylated epoxide 10d in 70% yield
(Scheme 1).
D-erythritol (16), which was prepared
D
With epoxides 10a, 10b, 10c, and 10d in hand, perbenzylated
thiosugar 18a was treated with them in the presence of tetrafluo-
roboric acid dimethyl ether complex (HBF4ꢀMe2O) at ꢁ60 °C. By the
regioselective attack of the thiosugar to the less hindered side of
the epoxides, from epoxide 10a was obtained predominantly the
Finally,
pounds 9a, 9b, 9c, and 9d were tested for small intestinal
-glucosidases in vitro,15 and compared with those of salacinol
a-glycosidase inhibitory activities of synthesized com-
a
(1), neosalacinol (5) and currently used antidiabetics (voglibose
and acarbose). (Table 2) All the molecules synthesized showed
ꢁ
corresponding coupled product (19a) with BF4 as the counter an-
ion, which was then exchanged with Clꢁ by treatment with ion ex-
change resin IRA-400 J (Clꢁ form) to give the corresponding
chloride 19a13 in 88% yield. Finally, hydrogenolysis of chloride
19a with palladium on carbon was carried out in 80% aqueous ace-
tic acid at 50–60 °C, where concomitant formation of partially acet-
ylated products was observed. Therefore, the crude product was
subjected to acidic methanolysis to give the target compound
9a14 in 72% yield from 18a. In a similar manner, epoxides 10b
and 10c were converted to 9b and 9c, respectively, in good yields.
On the other hand, the coupling reaction between epoxide 10d
with PMB ether of thiosugar (18b) resulted in a formation of a
complex mixture, by the careful chromatography of which the tar-
get compound 9d could be obtained in 15% yield.
Table 1
13C NMR data of neosalacinol6b (5) and compounds 9a–9d
5
9aa
9bb
9cb
9da
C1
C2
C3
C4
C5
C10
C20
C30
C40
52.1
79.4
79.5
73.7
61.0
51.8
69.6
75.3
64.0
52.1
79.4
79.5
73.7
61.0
51.8
68.6
85.1
60.0
52.1
79.4
79.5
73.7
61.1
51.8
68.7
83.5
60.8
52.2
79.5
79.6
73.8
61.1
51.8
68.8
83.7
60.8
52.1
79.4
79.6
73.7
61.0
51.8
68.7
82.8
60.7
All spectra were measured in CD3OD (a125 MHz, b175 MHz). Other signals: 9a: 58.5
(OCH3), 9b: 15.8 (OCH2CH3), 67.2 (OCH2CH3), 9c: 14.4 [OCH2(CH2)11CH3], 23.7/27.2/
30.4/30.6/30.7/31.0/33.0 [OCH2(CH2)11CH3], 72.0 [OCH2(CH2)11CH3], 9d: 73.5
(OCH2Ph), 129.0/129.4/129.5 (d, arom.), 139.4 (s, arom.).
The FAB-MS spectra of 9a, 9b, 9c, and 9d run in a positive mode
showed peaks at m/z 269, 283, 345, and 437, respectively, due to
the corresponding sulfonium cations. As shown in Table 1, 13C

G. Tanabe et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3159–3162
3161
the methyl as were exemplified in the present study would in-
crease the inhibitory activity of the molecule.
Further SAR studies in search for stronger a-glucosidase inhib-
itors of this sulfonium type of compounds are in progress.
OBn
OR
OH
3'
OH
H21C'
NOE
HO
OH
OBn
iii
O
S+
OR
Cl-
OR
10
H
S+
i
1
BnO
4
+
S
Acknowledgments
OBn
BnO
HO
OH
OH
BnO
19
9
This work was supported by ‘High-Tech Research Center’ Pro-
ject for Private Universities: matching fund subsidy from MEXT
(Ministry of Education, Culture, Sports, Science and Technology),
2007–2011, and also supported by a grant-in aid for scientific re-
search by the Japan society for the promotion of science (JSPS).
X = BF4
X = Cl
OBn
18a
BnO
ii
a : R = CH3, b : R = C2H5, c : R = C13H27
-
OH
BF4
OPMB
OBn
S
S+
OBn
PMBO
i
References and notes
HO
+
OPMB
O
PMBO
OH
HO
1. (a) de Melo, E. B.; Gomes, A.; Da, S.; Carvalho, I. Tetrahedron 2006, 62, 10277; (b)
Lillelund, V. H.; Jensen, H. H.; Liang, X.; Bols, M. Chem. Rev. 2002, 102, 515; (c)
Dwek, R. A. Chem. Rev. 1996, 96, 683; Iminosugars as Glycosidase Inhibitors:
Nojirimycin and Beyond; Stütz, A. E., Ed.; Wiley-VCH: Weinheim Germany,
1999.
2. (a) Yoshikawa, M.; Murakami, T.; Shimada, H.; Matsuda, H.; Yamahara, J.;
Tanabe, G.; Muraoka, O. Tetrahedron Lett. 1997, 38, 8367; (b) Yoshikawa, M.;
Morikawa, T.; Matsuda, H.; Tanabe, G.; Muraoka, O. Bioorg. Med. Chem. 2002, 10,
1547.
10d
18b
9d
Scheme 2. Reagents and conditions: (i) HBF4ꢀ(CH3)2O, CH2Cl2, ꢁ60 °C; (ii) IRA-400 J
(Clꢁ form), MeOH–H2O, rt; (iii) H2, Pd–C, 80% AcOH, 50–60 °C, then 10% aq
HCl–CH3OH (1:100, v/v), rt.
3. Yoshikawa, M.; Murakami, T.; Yashiro, K.; Matsuda, H. Chem. Pharm. Bull. 1998,
46, 1339.
4. Yoshikawa, M.; Xu, F.; Nakamura, S.; Wang, T.; Matsuda, H.; Tanabe, G.;
Muraoka, O. Heterocycles 2008, 75, 1397.
5. (a) Jayakanthan, K.; Mohan, S.; Pinto, B. M. J. Am. Chem. Soc. 2009, 131, 5621; (b)
Johnston, B. D.; Jensen, H. H.; Pinto, B. M. J. Org. Chem. 2006, 71, 1111; (c)
Tanabe, G.; Sakano, M.; Minematsu, T.; Matusda, H.; Yoshikawa, M.; Muraoka,
O. Tetrahedron 2008, 64, 10080; (d) Muraoka, O.; Xie, W.; Osaki, S.; Kagawa, A.;
Tanabe, G.; Amer, M. F. A.; Minematsu, T.; Morikawa, T.; Yoshikawa, M.
Tetrahedron 2010, 66, 3717.
OH OH
OH
Cl-
S+
OH
OCH3
HO
OH
HO
3'-O-methylneoponkoranol (20)
6. (a) Minami, Y.; Kuriyama, C.; Ikeda, K.; Kato, A.; Takebayashi, K.; Adachi, I.;
Fleet, G. W. J.; Kettawan, A.; Okamoto, T.; Asano, N. Bioorg. Med. Chem. 2008, 16,
2734; (b) Tanabe, G.; Yoshikai, K.; Hatanaka, T.; Yamamoto, M.; Shao, Y.;
Minematsu, T.; Muraoka, O.; Wang, T.; Matsuda, H.; Yoshikawa, M. Bioorg. Med.
Chem. 2007, 15, 3926; (c) Tanabe, G.; Xie, W.; Ogawa, A.; Cao, C.; Minematsu, T.;
Yoshikawa, M.; Muraoka, O. Bioorg. Med. Chem. Lett. 2009, 19, 2195.
7. (a) Ozaki, S.; Oe, H.; Kitamura, S. J. Nat. Prod. 2008, 71, 981; (b) Oe, H.; Ozaki, S.
Biosci. Biotechnol. Biochem. 2008, 72, 1962; (c) Muraoka, O.; Xie, W.; Tanabe, G.;
Amer, M. F. A.; Minematsu, T.; Yoshikawa, M. Tetrahedron Lett. 2008, 49, 7315.
8. Xie, W.; Tanabe, G.; Akaki, J.; Morikawa, T.; Ninomiya, K., Minematsu, T.,
Yoshikawa, M.; Wu, X.; Muraoka, O. Bioorg. Med. Chem. 2011, 19, 2015.
9. Recent review relevant to the work: (a) Mohan, S.; Pinto, B. M. Carbohydr. Res.
2007, 342, 1551; (b) Tanabe, G.; Matsuoka, K.; Minematsu, T.; Morikawa, T.;
Ninomiya, K.; Matsuda, H.; Yoshikawa, M.; Murata, H.; Muraoka, O. J. Pharm.
Soc. Jpn. 2007, 127(Suppl. 4), 129; (c) Nasi, R.; Patrick, B. O.; Sim, L.; Rose, D. R.;
Pinto, B. M. J. Org. Chem. 2008, 73, 6172; (d) Tanabe, G.; Hatanaka, T.;
Minematsu, T.; Matsuda, H.; Yoshikawa, M.; Muraoka, O. Heterocycles 2009, 79,
1093; (e) Mohan, S.; Jayakanthan, K.; Nasi, R.; Kuntz, D. A.; Rose, D. R.; Pinto, B.
M. Org. Lett. 2010, 12, 1088; (f) Sim, L.; Jayakanthan, K.; Mohan, S.; Nasi, R.;
Johnston, B. D.; Pinto, B. M.; Rose, D. R. Biochemistry 2010, 49, 443; (g)
Nakamura, S.; Takahira, K.; Tanabe, G.; Morikawa, T.; Sakano, M.; Ninomiya, K.;
Yoshikawa, M.; Muraoka, O.; Nakanishi, I. Bioorg. Med. Chem. Lett. 2010, 20,
4420; (h) Eskandari, R.; Kuntz, D. A.; Rose, D. R.; Pinto, B. M. Org. Lett. 2010, 12,
1632; (i) Eskandari, R.; Jayakanthan, K.; Kuntz, D. A.; Rose, D. R.; Pinto, B. M.
Bioorg. Med. Chem. 2010, 18, 2829; (j) Eskandari, R.; Jones, K.; Rose, D. R.; Pinto,
B. M. Bioorg. Med. Chem. Lett. 2010, 20, 5686. and references cited therein.
10. Abushanab, E.; Vemishetti, P.; Leiby, R. W.; Singh, H. K.; Mikkilineni, A. B.; Wu,
D. C.-J.; Saibaba, R.; Panzica, R. P. J. Org. Chem. 1988, 53, 2598.
Table 2
IC50 Values
antidiabetics against disaccharidases
(
l
M) of salacinol (1), neosalacinol (5), compounds 9a–9d, and two
Entry
Compound
Sucrase
Maltase
Isomaltase
1
2
3
4
5
6
7
8
1
5
9a
9b
9c
9d
Voglibose
Acarbose
1.6a
1.3a
0.46
0.12
1.3
5.2a
8.0a
5.3
1.7
1.0
1.3a
0.3a
0.39
0.27
0.95
0.14
2.1
0.32
0.2
0.44
1.2
1.5b
1.7b
646b
a
4
Lit.
Lit.
b
16
equal or considerably higher inhibitory activity than the refer-
ences. Against sucrase, all of them were found more active than
original sufonate (1), and 9b showed the highest inhibitory activity
of ca. ten times as potent as 1. It is noteworthy that, against mal-
tase, 9d was ca. ten times more potent than 1, and exerted superior
inhibitory activity to both acarbose and voglibose. The molecule is
the most potent inhibitor among this type of molecules so far.
Thus, it was concluded that higher hydrophobic property was pre-
ferred as the substituent on C30 for higher inhibitory activity. The
enhanced inhibitory activity encountered in the case of 9d would
11. For the enantiomer of 12, see: Marco, J. A.; Carda, M.; González, F.; Rodríguez,
S.; Murga, J. Liebigs Ann. 1996, 1801.
12. Vijayasaradhi, S.; Beedimane, M. N.; Aidhen, I. S. Synthesis 2005, 2267.
13. Synthesis of 19a: To a mixture of epoxide 10a (100 mg, 0.48 mmol), thiosugar
18a (168 mg, 0.4 mmol), and CH2Cl2 (2 ml) was added tetrafluoroboric acid
dimethyl ether complex (HBF4ꢀ(CH3)2O, 63 ll, 0.52 mmol) at ꢁ60 °C. The
reaction mixture was stirred for 3 h and concentrated in vacuo. The residue
was treated with ion exchange resin IRA-400 J (Clꢁ form) in methanol (3 ml)
at room temperature. Removal of the solvent left an oil (290 mg), which
on column chromatography (CHCl3 ? CHCl3–MeOH, 100:1 ? 50:1), gave
1,4-dideoxy-2,3,5-tri-O-benzyl-1,4-[(R)-[(2S,3S)-4-benzyloxy-2-hydroxy-3-
be ascribed to
p/p or CH/p
interactions17 of the phenyl ring at
C30 with surrounding aromatic residues of the active site in the
enzyme.
methoxybutyl]episulfoniumylidene]-
D
-arabinitol chloride (19a, 234 mg, 88%)
ꢁ7.3 (c = 0.65, CHCl3). IR (neat): 3174, 1454, 1404, 1365,
1H NMR (500 MHz, CDCl3) d: 3.41 (3H, s, OCH3),
as a colorless oil, ½a D24
ꢂ
1261, 1095, 1072, 1030 cmꢁ1
.
Eskandari et al. have reported very recently the synthesis and
evaluation of 30-O-methylneoponkoranol (20), and mentioned that
replacement of the sulfonate moiety with methyl group did not
contribute to the improvement of the inhibitory activity against
ntMGAM.9j We presume that the more hydrophobic moieties than
3.66–3.70 (2H, m, H-30 and H-40a), 3.76 (2H, d-like, J = ca. 8.0 Hz, H-5a and H-
5b), 3.80 (1H, dd, J = 11.5, 3.8 Hz, H-40b), 4.10 (1H, dd, J = 12.6, 3.7 Hz, H-10a),
4.11–4.15 (2H, m, H-1a and H-4), 4.15 (1H, dd-like, J = ca. 12.6, 7.4 Hz, H-10b),
4.17-4.18 (1H, m, H-3), 4.31 (1H, dd, J = 13.2, 3.8 Hz, H-1b), 4.34–4.39 (1H, m,
H-20), 4.39–4.41 (1H, m, H-2), 4.39 (1H, d, J = 11.7 Hz, OCH2Ph), 4.47–4.61 (7H,

3162
G. Tanabe et al. / Bioorg. Med. Chem. Lett. 21 (2011) 3159–3162
m, OCH2Ph), 6.65 (1H, br s, OH), 7.13–7.37 (20H, m, arom.). 13C NMR (125 MHz,
glucosidase of maltase, sucrase, and isomaltase. Test compound was dissolved
in dimethylsulfoxide (DMSO), and the resulting solution was diluted with
0.1 M maleate buffer to prepare the test compound solution (concentration of
DMSO:10%). The substrate solution in maleate buffer (maltose, 74 mM,
CDCl3) d: 48.4 (C-1), 51.9 (C-10), 57.9 (OCH3), 66.1 (C-4), 66.9 (C-5), 67.4 (C-40),
68.1 (C-20), 71.9/72.3/73.6(2xC) (OCH2Ph), 82.0 (C-30), 82.3 (C-3), 82.4 (C-2),
127.7/127.8/127.96/127.99/128.2/128.3/128.4/128.5/128.56/128.6/128.7/
128.8 (d, arom.), 135.8/136.0/136.7/137.9 (arom.). FAB-MS m/z: 629 [MꢁCl]+
(pos.).
sucrose, 74 mM, isomaltose, 7.4 mM, 50
(25 L), and the enzyme solution (25 L) were mixed and incubated at 37 °C
for 30 min. After incubation, the solution was immediately heated by boiling
water for 2 min to stop the reaction, and was mixed with water (150 L).
lL), the test compound solution
l
l
14. Compound 9a: colorless oil. ½a D26
ꢂ
+ 2.1 (c = 1.97, CH3OH). IR (neat): 3333, 1651,
1408, 1261, 1084, 1053, 1026 cmꢁ1
.
1H NMR (500 MHz, CD3OD) d: 3.29 (1H,
l
ddd-like, J = ca. 6.0, 4.0, 4.0 Hz, H-30), 3.47 (3H, s, OCH3), 3.66 (1H, dd, J = 12.3,
4.0 Hz, H-40a), 3.73 (1H, dd, J = 12.9, 9.2 Hz, H-10a), 3.80 (1H, dd, J = 12.3, 4.0 Hz,
H-40b), 3.82 (1H, dd, J = 12.9, 3.4 Hz, H-10b), 3.85 (2H, d-like, J = ca. 2.3 Hz, H-1a
and H-1b), 3.92 (1H, dd, J = 10.9, 9.5 Hz, H-5a), 3.99 (1H, br dd-like, J = ca. 9.5,
4.9 Hz, H-4), 4.05 (1H, dd, J = 10.9, 4.9 Hz, H-5b), 4.20 (1H, ddd, J = 9.2, 6.0,
3.4 Hz, H-20), 4.36 (1H, dd, J = 2.3, 1.1 Hz, H-3), 4.62 (1H, dt, J = 2.3, 2.3 Hz, H-2).
13C NMR data are listed in Table 1. FAB-MS m/z: 269 [MꢁCl]+ (pos.), FAB-HRMS
m/z: 269.1059 (C10H21O6S requires 269.1059).
Glucose concentration was determined by the glucose–oxidase method. Final
concentration of DMSO in the test solution was 2.5% and no influence of DMSO
was detected on the inhibitory activity.
16. Muraoka, O.; Morikawa, T.; Miyake, S.; Akaki, J.; Ninomiya, K.;
Pongpiriyadacha, Y.; Yoshikawa, M. J. Nat. Med. 2011, 65, 142.
17. The CH/
p Interaction. Evidence, Nature, and Consequences; Marchard, A. P., Ed.;
Wiley-VCH: New York, 1998.
18. Kessler, M.; Acuto, O.; Storelli, C.; Murer, H.; Müller, M.; Semenza, G. Biochim.
Biophys. Acta 1978, 506, 136.
15. Rat small intestinal brush border membrane vesicles were prepared18 and its
suspension in 0.1 M maleate buffer (pH 6.0) was used as small intestinal
a-