Synthesis of hexopyranosyl pyrimidine homonucleosides

Article abstract of DOI:10.1080/00397911.2020.1836224

A simple and convenient methodology has been developed for the synthesis of novel hexopyranosyl pyrimidine homonucleosides and hexopyranosyl double-headed pyrimidine homonucleosides from the corresponding native sugars, d-glucose and d-mannose. Thus, hexo

Full text of DOI:10.1080/00397911.2020.1836224

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Synthesis of hexopyranosyl pyrimidine
homonucleosides
Vineet Verma , Vipin K. Maikhuri , Vinod Khatri , Ankita Singh & Ashok K.
Prasad
To cite this article: Vineet Verma , Vipin K. Maikhuri , Vinod Khatri , Ankita Singh & Ashok
K. Prasad (2020): Synthesis of hexopyranosyl pyrimidine homonucleosides, Synthetic
Communications, DOI: 10.1080/00397911.2020.1836224
To link to this article: https://doi.org/10.1080/00397911.2020.1836224
View supplementary material
Published online: 25 Oct 2020.
Submit your article to this journal
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at
https://www.tandfonline.com/action/journalInformation?journalCode=lsyc20

V
R
SYNTHETIC COMMUNICATIONS
https://doi.org/10.1080/00397911.2020.1836224
Synthesis of hexopyranosyl pyrimidine homonucleosides
a
a
a,b
a
Vineet Verma , Vipin K. Maikhuri , Vinod Khatri , Ankita Singh , and
a
Ashok K. Prasad
a
b
Bioorganic Laboratory, Department of Chemistry, University of Delhi, Delhi, India; Department of
Chemistry, Pt. Neki Ram Sharma Govt. College, Rohtak, India
ABSTRACT
ARTICLE HISTORY
A simple and convenient methodology has been developed for the
synthesis of novel hexopyranosyl pyrimidine homonucleosides and
hexopyranosyl double-headed pyrimidine homonucleosides from the
corresponding native sugars, D-glucose and D-mannose. Thus, hexose
sugars were converted to 2,6-anhydro-3,4,5,7-tetra-O-benzyl-heptitols
and 2,6-anhydro-3,4,5-tri-O-benzyl-heptitols by recently developed
procedure of Khatri et al. Further, mono- and di-hydroxy 2,6-anhy-
dro-heptitols were converted to their corresponding mono- and di-
tosylated derivatives, which were then translated into hexopyranosyl
homonucleosides and double-headed homonucleosides by reaction
with uracil and thymine in 40–50 and 27–73% overall yields from
tetra- and tri-O-benzylated anhydro-heptitols.
Received 11 June 2020
KEYWORDS
2
,6-Anhydro-heptitols; hexo-
pyranosyl double-headed
homonucleosides; hexopyra-
nosyl homonucleosides;
hexopyranosyl pyrimidine
homonucleosides
GRAPHICAL ABSTRACT
Introduction
Modified nucleosides display a broad range of activities, such as anticancer, anti-HIV,
[
1–4]
antiviral, antiproliferative, and so forth.
Most of these molecules exert therapeutic
activities by imitating their physiological counterparts in order to exploit
cellular machinery and can be subsequently incorporated into DNA or RNA to inhibit
[
5]
[6]
cell division and viral replication. Herdewijn et al. synthesized building blocks of
b-D-homo-DNA, i.e., pyranosyl uracil 1a and adenine 1b which on inclusion into oligo-
nucleotides culminated in the discovery of new family of hexitol nucleic acids
[
7]
(Figure 1).
Further, double-headed nucleosides are defined as nucleosides containing two nucleo-
bases which can be used as building blocks for functionalized nucleic acids. These
chemically modified double-headed nucleosides can be used in automated solid-phase
synthesis to generate nucleic acids involving them and also for the synthesis of various
[
8–10]
functional materials.
As these double-headed nucleosides contain an additional
CONTACT Ashok K. Prasad
ashokenzyme@gmail.com
Bioorganic Laboratory, Department of Chemistry, University
of Delhi, Delhi, India.
Supplemental data for this article can be accessed on the publisher’s website.
ß 2020 Taylor & Francis Group, LLC

2
V. VERMA ET AL.
Figure 1. Examples of hexopyranosyl/furanosyl nucleosides and double-headed nucleosides/
homonucleosides.
nucleobase in same nucleoside unit, they may convey twice the amount of information
[
10–12]
than their single-headed counterpart when introduced in DNA strand.
Such
nucleosides might stabilize secondary structures, like bulges or three-way junctions by
[
13,14]
[15]
including two base-pairing options at one nucleotide site.
Kumar et al.
synthe-
sized double-headed furanosylnucleosides 2a and 2b, which were found to extend the
[
16,17]
duplex with an additional base pair (Figure 1). Herdewijn and coworkers
synthe-
sized double-headed nucleosides 2c and 2d with thymine and adenine nucleobases
which provides extra stability to DNA duplex due to extra base pairing in the minor
[
18]
groove of the duplex. Nielsen et al.
performed thermal hybridization studies with
double-headed nucleosides 2e and 2f in which additional nucleobase were connected via
0
methylene or ethylene linker in 5 (S)-C position of thymidine. The study clarified that
there are inter-strand stacking interactions due to these additional nucleobases in the
minor groove, which decreases upon increasing the length of linker. Recently, a novel
0
series of 3 -C-(1,4-disubstituted-1,2,3-triazolyl)double-headed hexopyranosyl nucleosides
2
[
19]
g–i have been synthesized and evaluated for their biological activities (Figure 1).
Herein, we report a simple and convenient methodology for the synthesis of novel hex-
opyranosyl pyrimidine homonucleosides and hexopyranosyl double-headed pyrimidine
homonucleosides from D-glucose and D-mannose.
Results and discussion
The sugar precursor for the synthesis of hexopyranosyl pyrimidine homonucleosides
was 2,6-anhydro-3,4,5,7-tetra-O-benzyl-heptitols 3a–3b, which were synthesized from D-
[
20]
glucose and D-mannose following the recently developed method of Khatri et al.
in
52 and 41% over all yields, respectively. The monohydroxy 2,6-anhydro-heptitols 3a
and 3b were treated with tosyl chloride in pyridine and the resulted monotosylated hep-
titols 4a and 4b were, in turn reacted with uracil (5a) and thymine (5b) in DMF in the
presence of 18-Crown-6 and potassium carbonate to afford tetra-O-benzylated hexopyr-
anosyl uracil and thymine homonucleosides 6a–d in 61 to 65% yields in two steps
(Scheme 1).

V
R
SYNTHETIC COMMUNICATIONS
3
Scheme 1. Synthesis of hexopyranosyl pyrimidine homonucleosides 7a–d.
Table 1. Optimization of the condition for the reaction of monotosylated 2,6-anhydro-glucoheptitol
a
4
a with uracil (5a) to synthesize benzylated hexopyranosyl methyl-uracil 6a .
b
ꢀ
c
S. No.
Base
Solvent
Catalyst
Temp. ( C)
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
9
1
1
1
1
a
.
.
.
.
.
.
.
.
K
K
K
K
2
2
2
2
CO
CO
CO
CO
3
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
H O
2
DMSO
DMF:DMSO (1:1)
DMF
DMF
18-Crown-6
18-Crown-6
18-Crown-6
18-Crown-6
18-Crown-6
18-Crown-6
18-Crown-6
18-Crown-6
18-Crown-6
18-Crown-6
18-Crown-6
TBABr
25
70
90
130
90
90
90
90
90
90
90
90
90
14
14
12
14
12
12
12
12
14
14
14
20
14
30
50
70
50
50
40
0
40
20
30
50
30
0
3
3
3
Na
Cs
NEt
t-BuOK
K
K
K
K
K
2
CO
3
2
CO
3
3
.
2
CO
2
CO
2
CO
2
CO
2
CO
3
3
3
3
3
0.
1.
2.
3.
–
Reactions were conducted with 4a (1 mmol) and uracil (1.5 mmoles) in solvent (8 ml) at temperature ranging from 25
ꢀ
to 130 C under N
2
-atmosphere.
b
c
Three equiv. of K
Isolated yield.
2
CO was used in all cases.
3
One of the reactions of monotosylated 2,6-anhydro-glucoheptitol with pyrimidine
base was tried at different temperatures, in presence of different bases, i.e., K CO ,
2
3
Na CO , Cs CO , t-BuOK, and NMe , and in different solvents, i.e., DMF, H O,
2
3
2
3
3
2
DMSO, and in DMF:DMSO (1:1). But in all cases, other than the reaction in DMF in
ꢀ
the presence of K CO and 18-Crown-6 as catalyst at 90 C, either the yields were less
2
3
or product formation was not observed (Table 1). There was an increase in yield of the
ꢀ
ꢀ
product when the temperature was increased from 25 C to 90 C because of the
increase in solubility of K CO in DMF with the increase in temperature but the yield
2
ꢀ
3
suddenly dropped at 130 C which may be attributed to decrease in complex formation
[
21]
between 18-Crown-6 and K CO at this temperature.
The use of K CO as a base
2 3
2
3
resulted in higher yield than Na CO or Cs CO because the complex formed between
2
3
2
3
þ
K ion and 18-Crown-6 is more stable than complex formed between 18-Crown-6 and
[
22]
other alkali metal ions.
butylammonium bromide (TBABr) in place of 18-Crown-6 and also in the absence of
8-Crown-6 led to the formation of product in 30% and 0% yields, respectively. This
The same reaction when performed in the presence of tetra-
1
may be attributed to relatively lesser solubility of TBABr in DMF than 18-Crown-6 and
reduction of basicity of K CO in the absence of 18-Crown-6, respectively. These results
2
3
are in conformity with polar aprotic nature of DMF that efficiently assisted removal of
tosyl group in heptitols by nucleobases in S 2 reaction fashion. There was an increase
N

4
V. VERMA ET AL.
in yield of the products when polar aprotic solvents were used rather than polar protic
solvents like H O because tosyl groups in heptitols were substituted by nucleobases via
2
SN2 mechanism. Further, DMF is a solvent of choice over DMSO because the solvation
of 18-Crown-6 with DMF is lesser than with DMSO. Therefore, 18-Crown-6 is more
easily available for complex formation with K CO in DMF than in DMSO which
2
3
resulted in higher formation constant for the complex formed between 18-Crown-6 and
[
23]
K CO in DMF than in DMSO.
2
3
The isomeric hexopyranosyl homonucleosides that may form due to attachment from
N3 position of pyrimidine nucleobases were not isolated in any of the cases. This may
be because of its lower nucleophilicity and higher steric hindrance. Further, debenzyla-
tion of hexopyranosyl homonucleosides 6a–d with 10% palladium-charcoal in methanol
under H atmosphere led to the formation of 1-(b-D-glucopyranosyl)methyl-uracil (7a),
2
1-(b-D-glucopyranosyl)methyl-thymine (7 b), 1-(b-D-mannopyranosyl)methyl-uracil (7c)
and 1-(b-D-mannopyranosyl)methyl-thymine (7d) in 80%, 78%, 80%, and 80% yields,
respectively.
The sugar precursor for the synthesis of hexopyranosyl double-headed pyrimidine
homonucleosides was dihydroxy 2,6-anhydro-3,4,5-tri-O-benzyl-heptitols 8a–b which, in
turn were obtained by selective removal of primary O-benzyl group from 2,6-anhydro-
3
,4,5,7-tetra-O-benzyl-heptitols 3a–3b using TFA-acetic anhydride/sodium methoxide-
[
20]
methanol.
The dihydroxy 2,6-anhydro-heptitols 8a and 8b were treated with three
equivalents of tosyl chloride in pyridine followed by the reaction of the resulted ditosy-
lated heptitols 9a and 9b with uracil (5a) and thymine (5b) in DMF in the presence of
ꢀ
1
8-Crown-6 and K CO at 90 C to afford tri-O-benzylated hexopyranosyl double-
2
3
headed homonucleosides 10a–c in 58% to 90% yields in two steps (Scheme 2). The
reaction of ditosylated 2,6-anhydro-mannoheptitol 9b with thymine (5b) under identical
condition led to the formation of complex mixture and the corresponding hexopyrano-
syl thymine double-headed homonucleosides 10d could not be isolated in pure form
even after many attempts. The debenzylation of homonucleosides 10a–c with 10% palla-
0
dium-charcoal in methanol under H atmosphere led to the formation of 1-[6 -deoxy-
2
0
0 0
6
-(uracil-1-yl)-b-D-glucopyranosyl]methyl-uracil (11a), 1-[6 -deoxy-6 -(thymin-1-yl)-
b-D-glucopyranosyl]methyl-thymine (11b), and 1-[6 -deoxy-6 -(uracil-1-yl)-b-D-manno-
pyranosyl]methyl-uracil (11c) in 80%, 70%, and 72% yields, respectively.
0
0
Structures of all synthesized intermediates and targeted hexopyranosyl pyrimidine
homonucleosides and hexopyranosyl double-headed pyrimidine homonucleosides, i.e.,
3
a–b, 4a–b, 6a–d, 7a–d, 8a–b, 9a–b, 10a–c, and 11a–c were unambiguously established
1
13
on the basis of their spectral ( H, C NMR, IR spectra and HRMS) data analysis.
Structures of known compounds, i.e., 3a–b and 8a–b were further confirmed by com-
[
20]
parison of their spectral data with those reported in the literature.
Conclusion
The present methodology describes a simple procedure for the synthesis of fourteen
novel benzylated and corresponding hydroxylhexopyranosyl pyrimidine homonucleo-
sides and hexopyranosyl double-headed pyrimidine homonucleosides from 2,6-anhydro-
heptitols derived from D-glucose and D-mannose. The notable features of the developed

V
R
SYNTHETIC COMMUNICATIONS
5
Scheme 2. Synthesis of hexopyranosyl double-headed homonucleosides 11a–c.
procedure are mild reaction conditions, excellent regioselectivity, and simplicity in oper-
ation. The high catalytic nature of 18-Crown-6 would make this method an attractive
alternative over existing methods.
Experimental
General procedure for the synthesis of tetra-O-benzylated hexopyranosyl uracil
and thymine homonucleosides 6a–d
A mixture of monotosylated 2,6-anhydroheptitol 4a/4b (2.5 g, 3.5 mmol), uracil/thymine
(
0.59 g/0.66g, 5.25 mmol), K CO (1.38 g, 10 mmol) and 18-Crown-6 (0.92 g, 3.5 mmol)
2 3
ꢀ
in DMF (25 mL) was heated to 90 C for 12 h under N -atmosphere. On completion,
2
the reaction mixture was poured into ice-cold water and extracted with ethyl acetate
(
(
3 ꢁ 100 mL). The combined organic layer was washed with saturated NaCl solution
2 ꢁ 100 mL), separated ethyl acetate layer was dried over anhydrous Na SO , filtered,
2
4
and then concentrated at reduced pressure. The crude product thus obtained was puri-
fied over silica gel column with 40% ethyl acetate in petroleum ether as eluent to afford
the pure benzylated hexopyranosyl homonucleosides 6a–6d.
0
0
0
0
1
-(b-D-2 ,3 ,4 ,6 -Tetra-O-benzylglucopyranosyl)methyl-uracil (6a). It was obtained
ꢀ
as white solid (1.60 g) in 70% yield; mp: 124–126 C; R ¼ 0.31 (50% ethyl acetate in
f
3
0
ꢂ1
petroleum ether); [a]
¼ þ10.35 (c 0.02, MeOH); IR(cm , KBr): 3031, 2850, 1684,
D
1
1
1
2
4
473, 1393, and 1135; H NMR (400 MHz, CDCl ): d 3.20–3.31 (m, 3H), 3.41–3.46 (m,
3
H), 3.52–3.57 (m, 3H), 3.65 (t, 1H, J ¼ 8.9 Hz), 4.29 (dd, 1H, J ¼ 14.1, 2.1 Hz), 4.42 (s,
H), 4.50 (d, 1H, J ¼ 10.8 Hz), 4.61 (d, 1H, J ¼ 11.1 Hz), 5.42 (d, 1H, J ¼ 7.9 Hz),
.73–4.78 (m, 1H), 4.81 (s, 1H), 4.83–4.86 (m, 1H), 5.43 (d, 1H, J ¼ 7.9 Hz), 7.09–7.29
1
3
(m, 21 H) and 8.71 (s, 1H); C NMR (100.6 MHz, CDCl ): d 48.8, 68.7, 73.5, 74.8, 75.2,
3
7
5.7, 78.1, 78.5, 78.3, 87.0, 101.3, 127.8, 128.0, 128.1, 128.4, 128.6, 138.0, 146.2, 150.7
þ
and 163.6; HRMS-ESI-TOF-MS: m/z 649.2913 ([M þ H] ), calcd. for
þ
[
C H N O þH] 649.2908.
3
9
40 2 7
1
13
Full experimental details, H and
C NMR spectra can be found in the
“Supplementary material” section of this article’s webpage.
Acknowledgments
We are thankful to CIF-USIC, University of Delhi, for providing NMR spectral and HRMS
recording facility.

6
V. VERMA ET AL.
Funding
We are grateful to the University of Delhi for providing financial support under DU-DST Purse
grant. V.V., V.K.M. thanks CSIR, New Delhi and CFEES (DRDO), New Delhi, for the award of
Junior/Senior Research Fellowship, respectively.
References
[
1] Break, L. M.; Mohamed, M. A. M.; Al-Thubaiti, O. A. A.; Eibaih, F. E. M. Nucleosides 10:
Synthesis of New Derivatives of Pyrimidine Nucleosides of Expected Biological Activity.
IJOC 2019, 09, 107–120. DOI: 10.4236/ijoc.2019.93010.
[
2] Trznadel, R.; Singh, A.; Kleczewska, N.; Liberska, J.; Ruszkowski, P.; Celewicz, L. Synthesis
and in Vitro Anticancer Activity of New Gemcitabine-Nucleoside Analogue Dimers
Containing Methyltriazole or Ester-Methyltriazole Linker. Bioorg. Med. Chem. Lett. 2019,
2
9, 2587–2594. DOI: 10.1016/j.bmcl.2019.08.003.
[3] Li, X.; Dumbre, S. G.; Lescrinier, E.; Groaz, E.; Herdewijn, P. Synthesis and Conformation
of Pentopyranoside Nucleoside Phosphonates. J. Org. Chem. 2019, 84, 6589–6603. DOI:
10.1021/acs.joc.8b03178.
[4] Epple, R.; Kudirka, R.; Greenberg, W. A. Solid-Phase Synthesis of Nucleoside Analogues.
J. Comb. Chem. 2003, 5, 292–310. DOI: 10.1021/cc020087f.
[5] Jordheim, L. P.; Durantel, D.; Zoulim, F.; Dumontet, C. Advances in the Development of
Nucleoside and Nucleotide Analogues for Cancer and Viral Diseases. Nat. Rev. 2013, 12,
447–464. DOI: 10.1038/nrd4010.
[6] Aerschot Van, A.; Verheggen, I.; Hendrix, C.; Herdewijn, P. 1,5-Anhydrohexitol Nucleic
Acids, a New Promising Antisense Construct. Angew. Chem. Int. Ed. Engl. 1995, 34,
1
338–1339. DOI: 10.1002/anie.199513381.
7] Eschenmoser, A. Chemical Etiology of Nucleic Acid Structure. Science 1999, 284,
118–2124. DOI: 10.1126/science.284.5423.2118.
[
[
[
2
8] Malinovskii, V. L.; Wenger, D.; Haner, R. Nucleic Acid-Guided Assembly of Aromatic
Chromophores. Chem. Soc. Rev. 2010, 39, 410–422. DOI: 10.1039/b910030j.
9] Bandy, T. J.; Brewer, A.; Burns, J. R.; Marth, G.; Nguyen, T.; Stulz, E. DNA as
Supramolecular Scaffold for Functional Molecules: Progress in DNA Nanotechnology.
Chem. Soc. Rev. 2011, 40, 138–148. DOI: 10.1039/b820255a.
[
10] Deleavey, G. F.; Damha, M. Designing Chemically Modified Oligonucleotides for Targeted
Gene Silencing. J. Chem. Biol. 2012, 19, 937–954. DOI: 10.1016/j.chembiol.2012.07.011.
11] Hornum, M.; Sharma, P. K.; Jacobsen, C. R.; Kumar, P.; Petersen, M.; Nielsen, P.
Condensing the Information in DNA with Double-Headed Nucleotides. Chem. Commun.
[
2
017, 53, 9717–9720. DOI: 10.1039/c7cc05047j.
[
12] Sharma, P. K.; Kumar, P.; Nielsen, P. Double-Headed Nucleotides: Building Blocks for
New Nucleic Acid Architectures. Aust. J. Chem. 2016, 69, 1094–1101. DOI: 10.1071/
CH16021.
[
13] Christensen, M. S.; Madsen, C. M.; Nielsen, P. Synthesis and Modelling of DNA Junction
and Minor Groove Zipper Motifs Incorporating the Double-Headed Nucleoside 5’(S)-C-
(
thymine-1-ylmethyl)thymidine. Org. Biomol. Chem. 2007, 5, 1586–1594. DOI: 10.1039/
b700852j.
[
[
14] Pedersen, S. L.; Nielsen, P. Stabilisation of Nucleic Acid Secondary Structures by
Oligonucleotides with an Additional Nucleobase; Synthesis and Incorporation of 2ꢀ -Deoxy-
2ꢀ -C-(2-(Thymine-1-yl)Ethyl)Uridine. Org. Biomol. Chem. 2005, 3, 3570. DOI: 10.1039/
b510167k.
15] Kumar, S.; Steffansen, S. I.; Albaek, N.; Nielsen, P. Synthesis of Bicyclic Double-Headed
Nucleoside. Tetrahedron 2014, 70, 583–589. DOI: 10.1016/j.tet.2013.12.013.

V
R
SYNTHETIC COMMUNICATIONS
7
[
[
16] Wu, T.; Nauwelaerts, K.; Van Aerschot, A.; Froeyen, M.; Lescrinier, E.; Herdewijn, P.
Base-Base Interactions in the Minor Groove of Double-Stranded DNA. J. Org. Chem.
2
006, 71, 5423–5431. DOI: 10.1021/jo052194c.
17] Wu, T.; Froeyen, M.; Schepers, G.; Mullens, K.; Rozenski, J.; Busson, R.; Aerschot, A. V.;
Herdewijn, P. Synthesis and Stability of Oligonucleotides Containing Acyclic Achiral
Nucleoside Analogues with Two Base Moieties. Org. Lett. 2004, 6, 51–54. DOI: 10.1021/
ol0360647.
[
18] Andersen, C.; Sharma, P. K.; Christensen, M. S.; Pedersen, N. S.; Nielsen, P. Synthesis of
Double-Headed Nucleosides with the Additional Nucleobase in the 5ꢀ -C-Position. Nucleic
Acids Symp. Ser. 2008, 52, 275–276. DOI: 10.1093/nass/nrn139.
[
19] Kiritsis, C.; Manta, S.; Papasotiriou, I.; Argyropoulou, E. C.; Trakossas, S.; Balzarini, J.;
0
0
Komiotis, D. Synthesis and Biological Evaluation of 3 -C-ethynyl and 3 -C-(1,4-
Disubstituted-1,2,3-triazolo) Double-Headed Pyranonucleosides. Med. Chem. 2012, 8,
320–329. DOI: 10.2174/157340612800786624.
[
[
[
[
20] Khatri, V.; Kumar, A.; Singh, B.; Malhotra, S.; Prasad, A. K. Synthesis of b-C-
Glycopyranosyl Aldehydes and 2,6-Anhydro-Heptitols. J. Org. Chem. 2015, 80,
11169–11174. DOI: 10.1021/acs.joc.5b01933.
21] El-Dossoki, F. I. The Effect of 18-Crown-6 on the Solubility and Thermodynamic
Parameters of Li CO , Na CO , NaCl, CH COONa and KCl in Methanol and Ethanol.
2
3
2
3
3
Indian J. Chem. 2005, 44A, 1594–1596.
22] Kikuchi, Y.; Sakamoto, Y. Complex Formation of Alkali Metal Ions with 18-Crown-6 and
Its Derivatives in 1,2-Dichloroethane. Anal. Chim. Acta 2000, 403, 325–332. DOI: 10.
1016/S0003-2670(99)00648-0.
23] Solov’ev, V. P.; Strakhova, N. N.; Raevsky, O. A.; Rudiger, V.; Schneider, H. J. Solvents
Effects on Crown Ether Complexations. J. Org. Chem. 1996, 61, 5221–5226. DOI: 10.1021/
jo952250h.