Synthesis and biological activity of 4′-C-hydroxymethyl-2′ fluoro-D-arabinofuranosylpurine nucleosides

Article abstract of DOI:10.1081/NCN-100002421

A series of 4′-C-hydroxymethyl-2′-fluoro-D-arabinofuranosylpurine nucleosides was prepared and evaluated for cytotoxicity in human tumor cell lines. A convenient synthesis of the carbohydrate precursor 4-C-hydroxymethyl-3,5-di-O-benzoyl-2-fluoro-α-D-arabi

Full text of DOI:10.1081/NCN-100002421

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SYNTHESIS AND BIOLOGICAL ACTIVITY
OF 4′-C-HYDROXYMETHYL-2′-FLUORO-D-
ARABINOFURANOSYLPURINE NUCLEOSIDES
A. T. Shortnacy-Fowler a , K. N. Tiwari a , J. A. Montgomery a & J. A. Secrist III b
a Southern Research Institute, P.O. Box 55305, Birmingham, Alabama, 35255-5305, U.S.A.
b Southern Research Institute, P.O. Box 55305, Birmingham, Alabama, 35255-5305, U.S.A.
Published online: 07 Feb 2007.
To cite this article: A. T. Shortnacy-Fowler , K. N. Tiwari , J. A. Montgomery & J. A. Secrist III (2001): SYNTHESIS AND
BIOLOGICAL ACTIVITY OF 4′-C-HYDROXYMETHYL-2′-FLUORO-D-ARABINOFURANOSYLPURINE NUCLEOSIDES, Nucleosides,
Nucleotides and Nucleic Acids, 20:4-7, 747-750
To link to this article: http://dx.doi.org/10.1081/NCN-100002421
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NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS, 20(4–7), 747–750 (2001)
SYNTHESIS AND BIOLOGICAL ACTIVITY
OF 4ꢀ-C-HYDROXYMETHYL-2ꢀ-
FLUORO-D-ARABINOFURANOSYLPURINE
NUCLEOSIDES
A. T. Shortnacy-Fowler, K. N. Tiwari, J. A. Montgomery,
and J. A. Secrist III∗
Southern Research Institute, P.O. Box 55305, Birmingham,
Alabama 35255-5305
ABSTRACT
A series of 4ꢀ-C-hydroxymethyl-2ꢀ-fluoro-D-arabinofuranosylpurine nucleo-
sides was prepared and evaluated for cytotoxicity in human tumor cell lines. A
convenient synthesis of the carbohydrate precursor 4-C-hydroxymethyl-3,5-di-
O-benzoyl-2-fluoro-α-D-arabinofuranosyl bromide (13) was developed. Cou-
pling of 13 with the sodium salt of 2,6-dichloropurine led to five target purine
nucleosides.
In recent years, synthesis of new nucleosides has gained a lot of attention
because of their utility as anticancer and as antiviral agents. Lately, there has been
interest in 4ꢀ-substituted nucleosides as potential anticancer agents (1–5). It has
been shown that such a modification can be tolerated and that the structure either
enhances or retains the biological activity (2,3,5). This suggests that metabolism to
the triphosphate is likely occurring. Interest in the synthesis and anticancer activity
of new nucleosides has continued in recent years in our laboratories. Fludarabine
phosphate, which was developed in our laboratory (6), has been approved by FDA
for the treatment of refractory lymphocytic leukemia. Clofarabine (2-chloro-2ꢀ-
fluoroara-A), also developed in our laboratory (7), is currently in clinical trials.
∗Corresponding author.
747
ꢁ
C
Copyright 2001 by Marcel Dekker, Inc.
www.dekker.com

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SHORTNACY-FOWLER ET AL.
Scheme 1.
Based upon its structure, with a 2ꢀ-fluorine in the arabino configuration, we initiated
a program to systematically examine other carbohydrate modifications, especially
at the 4ꢀ-position.
Initially, we focused our attention on the synthesis of the 4ꢀ-C-hydroxymethyl
analogue of clofarabine and related compounds. Very few 4ꢀ-C-hydroxymethyl
nucleosides have been reported in the literature, and most of the work has been
limited to the synthesis of ribonucleosides and 2ꢀ-deoxynucleosides (8,9). No 4ꢀ-C-
hydroxymethyl-arabino or 2ꢀ-fluoroarabinonucleosides have been reported in the
literature. Towards that goal, we developed a route to a 4-C-hydroxymethyl-2-
fluoroarabinofuranose derivative and utilized it in the synthesis of certain purine
nucleosides containing that carbohydrate moiety.
Our route (Scheme 1) to this series was accomplished by preparing the 4-C-
hydroxymethyl derivative 13 of α-bromo sugar 2 (10). Compound 2 was converted
to 3 by the careful addition of NaOCH3 in MeOH at 0◦C. When bromo displace-
ment was complete, more NaOCH3 was added with the reaction continuing at room
temperature to provide deprotected 4. Benzylation of 4 to 5 followed by the selec-
tive removal of the primary benzyl ether (11) gave alcohol 6. A molecular sieve
catalyzed pyridinium chlorochromate oxidation (12) of 6 to aldehyde 7 followed by

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4ꢀ-SUBSTITUTED NUCLEOSIDES AS ANTICANCER AGENTS
749
Scheme 2.
reaction with formaldehyde in base (8) led to diol 8. The remaining benzyl group
was removed, and the product 9 was benzoylated to give 10. Acid hydrolysis of
the methyl group of 10 provided 11 as an anomeric mixture (2α:1β), which was
acetylated yielding 12 (3α:1β) (13). Reaction of 12 with excess HBr in acetic acid
gave the target 4-C-hydroxymethyl bromo sugar 13 (6α:1β) suitable for subsequent
coupling reactions.
Our route (Scheme 2) to the purine nucleosides began with the coupling of
2,6-dichloropurine and 13 using the sodium salt glycosylation procedure (14) to
give an 82% total yield of 9-isomers 14. Treatment of 14 with NaOCH3/MeOH
removed the benzoyl groups and replaced the 6-Cl with −OCH3 to give 15. Prepar-
ative TLC resolved 15β and 15α, which were reacted separately with ethanolic
ammonia at 80◦C to provide 16β and 16α. Conversion of 14 to 17 was done with
NaN3 in refluxing EtOH. When the reaction was cooled, 17β crystallized and 17α
remained in solution. After isolation, the separate anomers were hydrogenated to
give intermediates 18β and 18α. Deprotection with NaOCH3/MeOH led to 19β and
19α. Deamination of 19β occurred slowly with adenosine deaminase to produce
guanosine analogue 20β. Under the same conditions, 19α failed to deaminate.
The 4ꢀ-C-hydroxymethyl nucleosides (16α, 16β, 19α, 19β, 20β) were exam-
ined in vitro against a spectrum of human tumor systems. Only clofarabine ana-
logue (16β) showed slight cytotoxicity (IC50 ∼13 µM) in CCRF-CEM leukemia
cells.

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ACKNOWLEDGMENT
This investigation was supported by the National Cancer Institute, National
Institutes of Health (P01-CA34200).
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