H2SO4-silica-promoted 'on-column' removal of benzylidene, isopropylidene, trityl and tert-butyldimethylsilyl groups

Article abstract of DOI:10.1016/j.carres.2008.10.003

H₂SO₄-silica-promoted removal of benzylidene, isopropylidene, trityl and tert-butyldimethylsilyl groups from sugar derivatives was accomplished by following an 'on-column' protocol in a virtually waste-free condition.

Full text of DOI:10.1016/j.carres.2008.10.003

Carbohydrate Research 344 (2009) 145–148
Contents lists available at ScienceDirect
Carbohydrate Research
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Note
H2SO4-silica-promoted ‘on-column’ removal of benzylidene,
isopropylidene, trityl and tert-butyldimethylsilyl groups
*
Bimalendu Roy, Priya Verma, Balaram Mukhopadhyay
Indian Institute of Science Education and Research-Kolkata (IISER-K), HC-VII, Sector-III, Salt Lake City, Kolkata 700 106, India
a r t i c l e i n f o
a b s t r a c t
Article history:
H2SO4-silica-promoted removal of benzylidene, isopropylidene, trityl and tert-butyldimethylsilyl groups
from sugar derivatives was accomplished by following an ‘on-column’ protocol in a virtually waste-free
condition.
Received 8 August 2008
Received in revised form 24 September
2008
Accepted 7 October 2008
Available online 14 October 2008
Ó 2008 Elsevier Ltd. All rights reserved.
Dedicated to Professor Srinivasan
Chandrasekaran, Indian Institute of Science,
Bengaluru, India
Keywords:
Hydrolysis
H2SO4-silica
On-column
Protecting group manipulation is an integrated part of synthetic
carbohydrate chemistry.1 Among the other protecting groups,
acid-labile groups like benzylidene acetals,2 isopropylidene ketals,2
trityl3 and tert-butyldimethylsilyl (TBDMS)4 are used routinely for
the purpose of selective protection and deprotection. Orthodox re-
moval of these groups involves the use of protic5 or Lewis acids.6
Common reagents like AcOH, TFA, HCl, and HBr are good enough
for the removal of these groups. However, in many cases, these re-
agents are not compatible with other acid-labile protecting groups
and sometime affect the glycosidic linkages. Moreover, use of these
reagents leads to rigorous work-up and purification process to get
the pure product. Here, we report an H2SO4-silica7-promoted ‘on-
column’ protocol for the removal of benzylidene, isopropylidene
and trityl groups. The method is simple, much less time consum-
ing, devoid of any extraction process, and scalable virtually under
waste-free condition.
with n-hexane–EtOAc (1:1). The resulting compounds were col-
lected and compared by TLC with the hydrolyzed products from
a solution-phase reaction. The ‘on-column’ chemistry resulted in
the formation of the desired hydrolyzed product 2 in 76% yield
with 20% recovery of the starting compound 1. No other side prod-
uct was evident from the TLC. Repeating the experiment by
increasing the reaction time to 30 min resulted in 87% formation
of the hydrolyzed product 2, which was satisfactorily characterized
by 1H, 13C NMR, and mass spectrometry. It is worth noting that the
same column was used repeatedly and up to 3 cycles of operation,
no significant loss of efficiency was observed (see Fig. 1).
A series of benzylidene derivatives with various glycosides and
protecting groups were subjected to hydrolysis through this ‘on-
column’ protocol. In all cases, satisfactory yields were obtained
including the compound having p-methoxybenzylidene group (Ta-
ble 1, entry 7). The products were characterized by 1H, 13C NMR,
and mass spectrometry. Results of these reactions are summarized
in Table 1. A Scale-up reaction (5 g) proved to be accessible by
increasing the column size (45 cm ꢀ 3 cm). 5 g of compound 1
was converted to hydrolyzed compound 2 in 82% yield using a
column.
A glass column (30 cm ꢀ 1 cm) was packed with 20 g of silica
(60–120 mesh) with a top layer of H2SO4-silica (2 g) as the reaction
zone for the required hydrolysis. A solution of ethyl 2,3-di-O-benz-
yl-4,6-O-benzylidene-1-thio-b-D
-galactopyranoside (1)8 (500 mg)
in CH2Cl2 (0.5 mL) was carefully added on the top of the column
ensuring that the soaked volume remained within the reaction
zone. The column was allowed to stand for 15 min, and was eluted
Similarly, isopropylidene groups were also cleaved successfully
from sugar derivative having different types of other protecting
groups. Selective deprotection of the terminal isopropylidene
group in glucofuranose moiety was achieved in very good yield
without affecting the protecting groups (Table 2, entries 1–5). In
* Corresponding author. Tel.: +91 33 2337 6771; fax: +91 33 2334 8092.
E-mail address: sugarnet73@hotmail.com (B. Mukhopadhyay).
0008-6215/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2008.10.003

146
B. Roy et al. / Carbohydrate Research 344 (2009) 145–148
1. Experimental
Ph
O
O
1.1. General methods
O
SEt
BnO
All reagents and solvents were dried prior to use according to
OBn
standard methods.20 Commercial reagents were used without fur-
ther purification unless otherwise stated. Analytical TLC was per-
formed on Silica Gel 60-F254 (Merck or Whatman) with detection
by fluorescence and/or by charring following immersion in a 10%
ethanolic solution of sulfuric acid. 1H NMR and 13C NMR spectra
were recorded on a Bruker Avance spectrometer at 300 and
75 MHz, respectively, using Me4Si as internal standard, as
appropriate.
1
Reaction zone
(H2SO4-silica)
Purification zone
(Normal silica gel)
OH
HO
O
SEt
BnO
1.2. Preparation of H2SO4-silica
OBn
2
To a slurry of silica gel (10 g, 230–400 mesh) in dry diethyl ether
(50 mL) was added commercially available concd H2SO4 (1 mL),
and the slurry was shaken for 5 min. The solvent was evaporated
under reduced pressure resulting in free flowing H2SO4-silica,
which was dried at 110 °C for 3 h and used for the reactions.
Figure 1. H2SO4-silica-promoted ‘on-column’ removal of benzylidene group.
case of mannopyranose moiety also, the primary isopropylidene
group was cleaved successfully in good yield (Table 2, entry 6).
The same protocol was used for the selective removal of trityl
and TBDMS groups. De-O-tritylated products were formed satisfac-
torily in good yield in the presence of benzyl or benzoyl groups. In
a similar fashion, TBDMS group was also cleaved selectively from
sugar derivatives. The results from these reactions are summarized
in Table 3. In the presence of acetyl groups, obvious acyl migration
was observed, and the ratio of the desired product and the
migrated product was found to be ꢁ1:1.
1.3. General procedure for ‘on-column’ hydrolysis
A glass column (30 cm ꢀ 1 cm) was packed with 20 g of silica
(60–120 mesh) with a top layer of H2SO4-silica (2 g). Now a solu-
tion of starting material (500 mg) in 0.5 mL CH2Cl2 was charged
slowly. The system was allowed to stand for the time mentioned
in Tables 1–3. Then, the column was eluted with adequate mixture
of n-hexane and EtOAc to get the pure product.
It is worth noting that increasing reaction time did not show
significant improvement of yields. However, solution-phase reac-
tion with a slurry of H2SO4-silica showed 3% increase in yield for
entry 1 (Table 1). But to keep it simple, we followed the ‘on-
column’ route. Use of dry solvent or wet solvent did not show
any difference on the outcome.
1.4. Propargyl 2,3-di-O-acetyl-b-D-glucopyranoside (12)
1H NMR (CDCl3, 500 MHz): d 5.34 (t, 1H, J2,3, J3,4 9.5 Hz, H-3),
5.25 (d, 1H, J1,2 3.5 Hz, H-1), 5.14 (dd, 1H, J1,2 3.5, J2,3 9.5 Hz,
H-2), 4.42 (m, 2H, CH2–C„CH), 4.28 (m, 2H, H-4, H-6a), 4.15 (m,
2H, H-5, H-6b), 2.38 (t, 1H, J 1.0 Hz, CH2–C„CH), 2.23 (br s, 2H,
Table 1
Removal of benzylidene acetals from sugar derivatives
OR1
O
OR1
O
OR1
O
OR1
O
R2O
BnO
R2O
BnO
R2O
AcO
R2O
BzO
STol
STol
SEt
AcO
OBn
OBz
OBn
OMe
7 R1,R2 = benzylidene
3 R1,R2 = benzylidene
4 R1 = R2 = H
5 R1,R2 = benzylidene
6 R1 = R2 = H
1 R1,R2 = benzylidene
2 R1 = R2 = H
8 R1 = R2 = H
OMP
Me
BnO
O
OR1
OR1
OR1
O
R2O
BzO
O
O
O
R2O
AcO
R2O
AcO
OAc
BnO
OC8H17
O
BzO
BnO
R2O
OMe
NPhTh
OAc
O
13 R1,R2
= p-MeO-benzylidene
14 R1 = R2 = H
11 R1,R2 = benzylidene
12 R1 = R2 = H
9
R1,R2 = benzylidene
10 R1 = R2 = H
OR1
15 R1,R2 = benzylidene
16 R1 = R2 = H
Entry
Starting material
Product
Timea (min)
Yield (%)
Ref.
1
2
3
4
5
6
7
8
9b
1
3
5
7
2
4
6
8
10
12
14
16
2
30
30
30
30
30
30
20
45
30
87
83
88
79
85
82
81
89
82
11
9
10
11
12
9
11
13
15
1
14
11
a
Time denotes the standing time (reaction time) between addition of the starting material on the column and column elution.
The reaction performed on 5 g scale.
b

B. Roy et al. / Carbohydrate Research 344 (2009) 145–148
147
2 ꢀ OH), 2.08 (s, 3H, COCH3), 2.04 (s, 3H, COCH3). 13C NMR (CDCl3,
125 MHz): d 170.7 (COCH3), 170.5 (COCH3), 96.1 (C-1), 78.3, 75.3,
70.8, 69.5, 68.0, 67.7, 61.8, 55.3, 20.7 (COCH3), 20.6 (COCH3). HRMS
calcd for C13H18O8Na (M+Na): 325.0899; found m/z 325.0896.
Table 2
Removal of isopropylidene groups from sugar derivatives
R1O
O
R2O
R1O
R2O
R1O
R2O
O
O
O
O
O
O
O
O
BzO
HO
AcO
17 R1 = R2 = isopropylidene
18 R1 = R2 = H
19 R1 = R2 = isopropylidene 21 R1 = R2 = isopropylidene
20 R1 = R2 = H
22 R1 = R2 = H
R1O
R2O
O
O
R1O
R1O
O
O
O
R2O
O
O
O
R2O
OMP
O
O
BnO
27 R1 = R2 = isopropylidene
28 R1 = R2 = H
23 R1 = R2 = isopropylidene
24 R1 = R2 = H
25 R1 = R2 = isopropylidene
26 R1 = R2 = H
Entry
Starting material
Product
Timea (min)
Yield (%)
Ref.
1
2
3
4
5
6
17
19
21
23
25
27
18
20
22
24
26
28
30
30
30
30
30
20
83
81
88
86
80
73
8c
8c
8c
13
8c
8c
a
Time denotes the standing time (reaction time) between addition of the starting material on the column and column elution.
Table 3
Deprotection of trityl and TBDMS groups from sugar derivatives
OR
OR
O
O
OR
OR
O
O
BzO
BzO
O
BnO
BnO
BnO
BnO
O
O
BzO
BnO
BnO
O
OMe
OC8H17
O
29 R = trityl
30 R = H
35 R = trityl
36 R = H
31 R = trityl
32 R = H
33 R = trityl
34 R = H
O
OR
O
OR2
R1O
AcO
BzO
BzO
NH
O
OSE
BzO
37 R = TBDMS
38 R = H
N
O
OMe
RO
OAc
O
41 R1 = Ac, R2 = TBDMS
42a R1 = H, R2 = Ac
42b R1 = Ac, R2 = H
HO OH
OR
O
O
39 R = trityl
40 R = H
AcO
OMP
O
OR
O
O
AcO
AcO
Me
O
O
O
BnO
OMP
O
AcO
AcO
BnO
O
OAc
O
Me
O
AcO
OAc
AcO
AcO
OAc
45 R = TBDMS
46 R = H
43 R = TBDMS
44 R = H
Entry
Starting material
Product
Time (min)a
Yield (%)
Ref.
1
2
3
4
5
6
7
8
9
29
31
33
35
37
39
41
43
45
30
32
34
36
38
40
42a + 42b
44
46
20
20
20
20
30
20
30
30
30
82
80
83
85
79
81
83
81
84
14
15
16
17
18
19

148
B. Roy et al. / Carbohydrate Research 344 (2009) 145–148
1.5. p-Methoxyphenyl 2,3-di-O-benzyl-
a
-
D
-glucopyranosyl-
1H, J3,4 3.3 Hz, H-4), 5.23–5.11 (m, 2H, H-20, H-200), 5.05 (dd, 1H,
(1?3)-2-O-acetyl-4-O-benzyl-
a-
L-rhamnopyranoside (16)
J2 ,3 9.3 Hz, J3 ,4 3.0 Hz, H-30), 5.03 (m, 2H, H-1, H-300), 4.95 (d, 1H,
0
0
0
0
J1 ,2 7.8 Hz, H-10), 4.67 (d, 1H, J1 ,2 7.8 Hz, H-100), 4.29 (m, 1H, H-
3), 4.09–3.91 (m, 5H, H-2, H-5a, H-6a0, H-6a00, H-6b0), 3.76 (s, 3H,
C6H4OCH3), 3.57–3.48 (m, 4H, H-50, H-500, H-5b, H-6b00), 3.18 (br s,
1H, OH), 2.21 (s, 3H, COCH3), 2.20 (s, 3H, COCH3), 2.16 (s, 3H,
COCH3), 2.11 (s, 3H, COCH3), 2.10 (s, 3H, COCH3), 2.03 (s, 3H,
COCH3), 1.98 (s, 3H, COCH3), 1.96 (s, 3H, COCH3). 13C NMR
(75 MHz, CDCl3): d 169.8 (COCH3), 169.7 (COCH3), 169.7 (COCH3),
169.5 (COCH3), 169.5 (COCH3), 169.1 (COCH3), 169.1 (COCH3),
168.9 (COCH3), 154.8, 149.5, 118.2(2), 114.1(2) (ArC), 100.3 (C-
10), 100.1 (C-100), 97.9 (C-1), 78.0, 76.8, 76.4, 75.7, 74.5, 73.8, 73.2,
70.7, 68.8, 68.4, 66.9, 66.4, 62.5, 60.6, 55.0 (C6H4OCH3), 20.9
(COCH3), 20.9 (COCH3), 20.4 (COCH3), 20.4 (COCH3), 20.2 (COCH3),
20.2 (COCH3), 20.1 (COCH3), 20.1 (COCH3). HRMS calcd for
C40H56O24N (M+NH4): 934.3192; found 934.3193.
0
0
00 00
1H NMR (CDCl3, 300 MHz): d 7.42–7.28 (m, 15H, ArH), 6.97, 6.82
(2d, J 7.8 Hz, C6H4OMe), 5.55 (dd, 1H, J1,2 1.5, J2,3 1.8 Hz, H-2), 5.34
(d, 1H, J1,2 1.5 Hz, H-1), 5.20 (d, 1H, J1 ,2 3.3 Hz, H-10), 5.05–4.70
(6d, 6H, J 11.4 Hz, 3 ꢀ CH2C6H5), 4.33 (dd, 1H, J 3.3 Hz, 8.4 Hz),
3.91 (dd, 1H, J 1.5 Hz, 9.0 Hz), 3.87 (m, 2H), 3.78 (s, 3H, C6H4–
OCH3), 3.68–3.61 (m, 4H), 3.55 (dd, 1H, J 3.3 Hz, 9.6 Hz), 2.10 (br
s, 1H, OH), 1.99 (s, 3H, COCH3), 1.70 (br s, 1H, OH), 1.34 (d, 3H, J
6.3 Hz, C–CH3). 13C NMR (CDCl3, 75 MHz): d 170.5 (COCH3),
155.1, 150.0, 138.6, 138.0, 137.7, 128.5(2), 128.4(2), 128.3,
128.2(2), 127.9(2), 127.8(2), 127.6(2), 117.8(2), 114.6(2), 96.6 (C-
10), 93.0 (C-1), 96.6, 93.0, 81.0, 79.4, 79.2, 75.7, 75.0, 72.8, 72.2,
71.0, 70.3, 68.5, 67.8, 62.0 (C-60), 55.6 (C6H4OCH3), 20.7 (COCH3),
17.9 (C–CH3). HRMS calcd for C42H48O12Na (M+Na): 767.3043;
found m/z 767.3033.
0
0
Acknowledgments
1.6. Propargyl 2,3,4-tri-O-benzoyl-a-D-glucopyranoside (36)
B.R. and P.V. are thankful to CSIR, New Delhi and UGC, New Del-
hi, respectively, for providing fellowships. The present work is sup-
ported by DST Fast Track Grant (SR/FTP/CS-110/2005).
1H NMR (CDCl3, 500 MHz): d 8.11–7.26 (m, 15H, ArH), 6.15 (t, 1H,
J3,4, J4,5 10.0 Hz, H-4), 5.63 (t, 1H, J2,3, J3,4 10.0 Hz, H-3), 5.55 (d, 1H,
J1,2 3.5 Hz, H-1), 5.32 (dd, 1H, J1,2 3.5, J2,3 10.0 Hz, H-2), 4.35 (m,
3H, CH2–C„CH, H-5), 4.23 (dd, 1H, J5,6a 4.5, J6a,6b 12.5 Hz, H-6a),
4.14 (dd, 1H, J5,6b 2.0, J6a,6b 12.5 Hz, H-6b), 2.38 (t, 1H, J 1.5 Hz,
CH2–C„CH), 2.21 (br s, 1H, OH). 13C NMR (CDCl3, 125 MHz): d
165.8 (COC6H5), 165.7 (COC6H5), 165.3 (COC6H5), 133.5, 133.4,
133.1, 129.9(2), 129.8(2), 129.7(2), 128.4(2), 128.3(2), 128.2(2)
(ArC), 95.1 (C-1), 78.2, 75.4, 71.6, 70.2, 69.1, 68.2, 62.2, 55.7. HRMS
calcd for C30H26O9Na (M+Na): 553.1475; found m/z 553.1473.
References
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1.7. p-Methoxyphenyl 2,3,4-tri-O-acetyl–
(1?2)-3,4-di-O-benzyl– -rhamnopyranosyl-(1?2)-3,4-O-
isopropylidene-b- -galactopyranoside (44)
L-rhamnopyranosyl-
4. (a) Clark, J. H. Chem. Rev. 1980, 80, 429; (b) Corey, E. J.; Venkateswarlu, A. J. Am.
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L
D
5. (a) Choy, Y. M.; Unrau, A. M. Carbohydr. Res. 1971, 17, 439–443; (b) Bessodes,
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7. For the use of H2SO4-silica in carbohydrate modifications see: (a)
Mukhopadhyay, B. Tetrahedron Lett. 2006, 47, 4337–4341; (b) Rajput, V. K.;
Mukhopadhyay, B. Tetrahedron Lett. 2006, 47, 5939–5941; (c) Rajput, V. K.; Roy,
B.; Mukhopadhyay, B. Tetrahedron Lett. 2006, 47, 6987–6991; (d) Dasgupta, S.;
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½
a 2D5
ꢂ
+81 (c 1.0, CHCl3). 1H NMR (CDCl3, 300 MHz): d 7.55–7.47
(m, 10H, ArH), 7.19, 6.99 (2d, 4H, J 9.0 Hz, C6H4OCH3), 5.65 (dd, 1H,
J1 ,2 1.8 Hz, J2 ,3 3.3 Hz, H-200), 5.56 (dd, 1H, J2 ,3 3.3 Hz, J3 ,4
00 00
00 00
00 00
00 00
9.9 Hz, H-300), 5.49 (d, 1H, J1 ,2 1.8 Hz, H-100), 5.26 (t, 1H, J3 ,4
,
00 00
00 00
J4 ,5 9.9 Hz, H-400), 5.13, 4.94, 4.85, 4.79 (4d, 4H, J 11.7 Hz,
00 00
0
0
2 ꢀ CH2Ph), 5.10 (d, 1H, J1,2 6.3 Hz, H-1), 4.95 (d, 1H, J1 ,2 1.5 Hz,
H-10), 4.46–4.35 (m, 4H, H-20, H-3, H-500, H-6a), 4.24 (dd, 1H, J1,2
6.3 Hz, J2,3 9.9 Hz, H-2), 4.19–4.12 (m, 4H, H-4, H-5, H-50, H-6b),
4.04 (dd, 1H, J2 ,3 2.7 Hz, J3 ,4 9.3 Hz, H-30), 3.99 (s, 3H, C6H5OCH3),
0
0
0
0
3.79 (t, 1H, J3 ,4 , J4 ,5 9.6 Hz, H-40), 2.36 (s, 3H, COCH3), 2.31 (s, 3H,
COCH3), 2.26 (s, 3H, COCH3), 1.82 (s, 3H, isopropylidene-CH3), 1.57
0
0
0
0
00 00
(s, 3H, isopropylidene-CH3), 1.57 (d, 3H, J5 ,6 6.0 Hz, C–CH3), 1.45
(d, 3H, J5 ,6 6.3 Hz, C–CH3). 13C NMR (CDCl3, 75 MHz): d 169.6
(COCH3), 169.5 (COCH3), 169.4 (COCH3), 155.4, 151.5, 139.0,
138.5, 128.3(2), 128.2(2), 127.8(2), 127.4(2), 127.3(2), 117.9(2),
114.7(2) (ArC), 110.6 [C(CH3)2], 100.3 (C-1), 99.5 (C-100), 97.5 (C-
10), 80.1(2), 79.4, 75.1, 75.0, 73.8, 73.7, 72.3, 71.2, 69.9, 69.2, 68.4,
66.8, 62.2 (C-6), 55.5 (C6H4OCH3), 28.1 (isopropylidene-CH3), 26.6
(isopropylidene-CH3), 20.9 (COCH3), 20.8 (COCH3), 20.7 (COCH3),
18.1 (C–CH3), 17.2 (C–CH3). HRMS calcd for C48H60O18Na
(M+Na)+: 947.3677; found 947.3675.
0
0
9. Lin, C.-C.; Hsu, T.-S.; Lu, K.-C.; Huang, I.-T. J. Chin. Chem. Soc. 2000, 47, 921–928.
10. Yan, M.-C.; Chen, Y.-N.; Wu, H.-T.; Lin, C.-C.; Chen, C.-T.; Lin, C.-C. J. Org. Chem.
2007, 72, 299–302.
11. Whistler, R. L.; Kazeniac, S. J. J. Am. Chem. Soc. 1954, 76, 3044–3045.
12. Agnihotri, G.; Misra, A. K. Tetrahedron Lett. 2006, 47, 3653–3658.
13. Mereyala, H. B.; Goud, P. M.; Gadikota, R. R.; Maddala, R. K.; Reddy, K. R. J.
Carbohydr. Chem. 2000, 19, 1201–1210.
14. Takahashi, H.; Miyama, N.; Mitsuzuka, H.; Ikegami, S. Synthesis 2004, 2991–
2994.
15. Wing, C.; Errey, J. C.; Mukhopadhyay, B.; Blanchard, J. S.; Field, R. A. Org. Biomol.
Chem. 2006, 4, 3945–3950.
16. Roslund, M. U.; Klika, K. D.; Lehtilä, R. L.; Tähtinen, P.; Sillanpää, R.; Leino, R. J.
1.8. p-Methoxyphenyl 2,3,4-tri-O-acetyl-b-
(1?3)-4-O-acetyl-2-O-(2,3,4,6-tetra-O-acetyl-b-
galactopyranosyl)- -arabinopyranoside (46)
D-galactopyranosyl-
D-
Org. Chem. 2004, 69, 18–25.
a-
L
17. Verduyn, R.; Douwes, M.; van der Klein, P. A. M.; Mösinger, E. M.; van der
Marel, G. A.; van Boom, J. H. Tetrahedron 1993, 49, 7301–7316.
18. Commercially available.
19. Mukhopadhyay, B.; Field, R. A. Carbohydr. Res. 2006, 341, 1697–1701.
20. Perrin, D. D.; Amarego, W. L.; Perrin, D. R. Purification of Laboratory Chemicals;
Pergamon: London, 1996.
½
a 2D5
ꢂ
+107 (c 1.0, CHCl3). 1H NMR (300 MHz, CDCl3): d 6.96 (d,
2H, J 9.0 Hz, C6H4OCH3), 6.81 (d, 2H, J 9.0 Hz, C6H4OCH3), 5.43
(bd, 1H, J3 ,4 3.0 Hz, H-40), 5.36 (d, 1H, J3 ,4 3.3 Hz, H-400), 5.26 (d,
0
0
00 00