Pteridines Part CXVIII. Methanopterin, chemical approach and partial synthesis

Article abstract of DOI:10.1002/hlca.200790195

Our approach to achieve a partial synthesis of methanopterin (1) started from 6-acetyl-O⁴-isopropyl-7-methylpterin (20) which was obtained either by condensation from 6-isopropoxypyrimidine-2,4,5-triamine (19) and pentane-2,3,4-trione (6) or from 6-isopropoxy-5-nitrosopyrimidine-2,4-diamine (21) and pentane-2,4-dione (=acetylacetone; 22) (Scheme2). NaBH₄ reduction of 20 led to 6-(1-hydroxyethyl)-O⁴-isopropyl-7-methylpterin (23) which was converted into the corresponding 6-(1-chloroethyl) and 6-(1-bromoethyl) derivatives 24 and 25. A series of nucleophilic displacement reactions in the side chain and at position 4 were performed as model reactions to give 26-29, 32-35, and 39-41. Hydrolysis of the substituents at C(4) led to the corresponding pterin derivatives 30, 31, 36-38, and 42. Analogously, 25 reacted with 1-(4-aminophenyl)-1-deoxy-2,3:4,5-di-O-isopropylidene-D-ribitol (43), prepared from N-(4-bromophenyl)benzamide (47) via 49 and 50 to give 1-{4-{{1-[2-amino-7-methyl-4-(1-methylethoxy)pteridin-6-yl]ethyl}amino}phenyl} -1-deoxy-D-ribitol (44) in 62% yield (Scheme 3). Acid cleavage of the isopropylidene groups at room temperature led to 45 and on boiling to 1-{4-{[1-(2-amino-3,4-dihydro-7-methyl-4-oxopteridin-6-yl)ethyl]amino}phenyl} -1-deoxy-D-ribitol (46). The next step, however, attachment of the ribofuranosyl moiety with 55 or 56 to the terminal 1-deoxy-D-ribitol OH group could not been achieved. The second component, bis(4-nitrobenzyl) 2-{[(2-cyanoethoxy) (diisopropylamino)phosphino]oxy}pentanedioate (61), to built-up methanopterin (1) was synthesized from 2-hydroxypentanedioic acid (59) and worked well in another model reaction on phosphitylation with N⁶-benzoyl-2′, 3′-O-isopropylideneadenosine and oxidation to give 62 (Scheme 6).

Full text of DOI:10.1002/hlca.200790195

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Helvetica Chimica Acta – Vol. 90 (2007)
Pteridines
Part CXVIII1)
Methanopterin, Chemical Approach and Partial Synthesis
by Gerhard Heizmann and Wolfgang Pfleiderer*
Fachbereich Chemie, Universität Konstanz, Postfach 5560, D-78434 Konstanz
Our approach to achieve a partial synthesis of methanopterin (1) started from 6-acetyl-O4-isopropyl-
7-methylpterin (20) which was obtained either by condensation from 6-isopropoxypyrimidine-2,4,5-
triamine (19) and pentane-2,3,4-trione (6) or from 6-isopropoxy-5-nitrosopyrimidine-2,4-diamine (21)
and pentane-2,4-dione (¼acetylacetone; 22) (Scheme 2). NaBH4 reduction of 20 led to 6-(1-
hydroxyethyl)-O4-isopropyl-7-methylpterin (23) which was converted into the corresponding 6-(1-
chloroethyl) and 6-(1-bromoethyl) derivatives 24 and 25. A series of nucleophilic displacement reactions
in the side chain and at position 4 were performed as model reactions to give 26 – 29, 32 – 35, and 39 – 41.
Hydrolysis of the substituents at C(4) led to the corresponding pterin derivatives 30, 31, 36 – 38, and 42.
Analogously, 25 reacted with 1-(4-aminophenyl)-1-deoxy-2,3:4,5-di-O-isopropylidene-d-ribitol (43),
prepared from N-(4-bromophenyl)benzamide (47) via 49 and 50 to give 1-{4-{{1-[2-amino-7-methyl-4-(1-
methylethoxy)pteridin-6-yl]ethyl}amino}phenyl}-1-deoxy-d-ribitol (44) in 62% yield (Scheme 3). Acid
cleavage of the isopropylidene groups at room temperature led to 45 and on boiling to 1-{4-{[1-(2-amino-
3,4-dihydro-7-methyl-4-oxopteridin-6-yl)ethyl]amino}phenyl}-1-deoxy-d-ribitol (46). The next step,
however, attachment of the ribofuranosyl moiety with 55 or 56 to the terminal 1-deoxy-d-ribitol OH
group could not been achieved. The second component, bis(4-nitrobenzyl) 2-{[(2-cyanoethoxy)(diiso-
propylamino)phosphino]oxy}pentanedioate (61), to built-up methanopterin (1) was synthesized from 2-
hydroxypentanedioic acid (59) and worked well in another model reaction on phosphitylation with N6-
benzoyl-2’,3’-O-isopropylideneadenosine and oxidation to give 62 (Scheme 6).
1. Introduction. – Methanogenic bacteria comprise a very selected unique group of
microorganisms which derive their energy for growth from the hydrogen-dependent
reduction of CO2 to produce methane. In this process, a series of unique coenzymes are
involved which remind structurally 5,6,7,8-tetrahydrofolic acid functioning as a C1
carrier in the biosynthesis of serine, thymidylate, purines, and methionine. One of these
bacterial coenzymes is 5,6,7,8-tetrahydromethanopterin acting as C1 carrier in
methanogenesis. In the reduction steps at the formyl, hydroxymethyl, and methyl
level, this pterin derivative plays an important role and keeps the C1 unit bound during
these transformation processes. The biochemistry of methane production is known and
has been summarized [2].
Methanopterin (MPT; 1), an oxidation product of the natural coenzyme, was
isolated from Methanobacterium thermoautotrophicum and first described by Vogels
et al. [3] and its structure elucidated by the same research group [4]. The structure of
1
)
Part CXVII: [1].
ꢀ 2007 Verlag Helvetica Chimica Acta AG, Zürich

Helvetica Chimica Acta – Vol. 90 (2007)
1857
methanopterin (1) is complex and was identified as 1-{4-{[(1R)-1-(2-amino-3,4-
dihydro-7-methyl-4-oxopteridin-6-yl)ethyl]amino}phenyl}-1-deoxy-5-O-{5-O-{[(1S)-
1,3-dicarboxypropoxy]hydroxyphosphinyl}-a-d-ribofuranosyl}-d-ribitol in which the
phosphate group is esterified with a-hydroxyglutaric acid (¼2-hydroxypentanedioic
acid). Structural analogs have been found in Methanosarcina barkeeri, i.e., sarcinap-
terin (2) [5], in Methanogenium tationis, i.e., tatiopterin (3) [6], and in Methanocullens
thermophilicum, i.e., thermopterin (4) [7].
The structural relationship between methanopterin (1) and folic acid is obvious
since both molecules basically consist of a 2-aminopteridin-4(3H)-one (¼ pterin) and a
p-substituted benzenamine derivative connected to each other by a C-atom attached to
C(6) of the pterin and the amino group of the benzenamine moiety, respectively. Major
differences between MPTand folic acid concern the presence in MPTof two additional
Me groups at C(7) and at the linking C-atom as well as the extended side chain bound
to the benzene ring. The configuration of this side chain was identified as being that of a
1-deoxy-d-ribitol (¼d-ribityl) [8] moiety, the terminal hydroxy group of which is
connected to C(1) of a d-ribofuranose unit by an a-glycosidic linkage. Finally, C(5) of
this latter ribose moiety is phosphylated and connected to a-hydroxyglutaric acid.
2. Synthesis. – We decided to achieve the chemical synthesis of this interesting
natural product by approaching the composition from the side of the pterin moiety by
stepwise condensation reactions of various building units [9]. We started with a
Gabriel – Isay reaction [10] between 2,5,6-triaminopyrimid-4(3H)-one (5) and pen-
tane-2,3,4-trione (6) under neutral aqueous conditions to achieve a regioselective
condensation between the most nucleophilic 5-amino group and the 3-oxo group to the
intermediary Schiff base 7 which cyclized to 6-acetyl-7-methylpterin (8) [11]
(Scheme 1). Since 8 is a very insoluble compound, especially in organic solvents, we
improved solubility by acylation of the 2-amino group by acetic, isopropionic, and
pivaloic anhydride to give 9 – 11 in good yields.

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Helvetica Chimica Acta – Vol. 90 (2007)
Scheme 1
The NaBH4 reduction of 8 – 11 proceeded well to give the corresponding 6-(1-
hydroxyethyl)pterin derivatives 12 – 15 (Scheme 1). The interconversion of 8 to 6-(1-
bromoethyl)-7-methylpterin (16) with conc. HBr solution worked only in low yield,
whereas the reaction of 10 and 11 in CHCl3 with thionyl bromide gave 17 and 18,
respectively, in yields of 70– 90%.
All attempts to displace the Br-atom in 16 – 18 by primary amines were very
disappointing and let to complex mixtures from which no clean substances could be
isolated. We switched then to O4-alkylpterin derivatives which are known as readily
soluble substances [12]. The 6-isopropoxypyrimidine-2,4,5-triamine (19) was con-
densed with 6 to form 1-(2-amino-4-isopropoxy-7-methylpteridin-6-yl)ethanone (20) in
79% yield (Scheme 2). The same substance resulted also from a Timmis reaction
between 6-isopropoxy-5-nitroso-pyrimidine-2,4-diamine (21) and propane-2,4-dione
(¼acetylacetone; 22). Reduction of the oxo group of 20 by NaBH4 gave 23, and
subsequent treatment with SOCl2 and SOBr2 led to the valuable synthons 24 and 25,
respectively. Nucleophilic substitution reactions with 24 and aliphatic primary amines
such as propan-1-amine, neopentylamine (¼2,2-dimethylpropan-1-amine), and benzyl-
i
amine (¼ benzenemethanamine) in PrOH as solvent gave unexpected results. The
amines replaced the isopropoxy group in 4-position, and the Cl-atom in the side chain
was substituted by the isopropoxy residue leading to 26 – 28. In an analogous
experiment between 24 and neopentylamine in EtOH resulted 6-(1-ethoxyethyl)-7-
methyl-N4-neopentylpteridine-2,4-diamine (29). The structures of 26 – 29 were estab-
1
lished by H-NMR spectra and elemental analyses and further confirmed by basic
hydrolysis forming the corresponding pterin derivatives 30 and 31.

Helvetica Chimica Acta – Vol. 90 (2007)
1859
Scheme 2
The change from alcohol solvents to aprotic solvents like DMF or MeCN was some
kind of a break-through in our efforts since now primary aromatic amines like aniline
(¼ benzenamine), p-toluidine (¼4-methylbenzenamine) and ethyl 4-aminobenzoate

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Helvetica Chimica Acta – Vol. 90 (2007)
reacted with 25 in the expected manner substituting the Br-atom to form the
corresponding 6-[1-(arylamino)ethyl] derivatives 32 – 34 (Scheme 2). Excess of amine
and extended reaction time led to disubstitution as shown with 24 and p-toluidine
giving 35. Basic hydrolysis of 32 – 35 in 1n NaOH/dioxane again resulted in the
formation of the pterin derivatives 36 – 38. Furthermore, the Cl-atom in 24 was easily
displaced by alkoxy residues on treatment in the appropriate alcohol in the presence of
Et3N yielding 39 – 41. The subsequent hydrolysis in 1n NaOH led to the pterin
derivatives 30, 31, and 42.
Knowing the side-chain reactivity of 24 and 25, the next step was the introduction of
the 1-(4-aminophenyl)-1-deoxy-d-ribitol residue into 25 (Scheme 3). For this purpose,
we synthesized the 1-(4-aminophenyl)-1-deoxy-2,3:4,5-di-O-isopropylidene-d-ribitol
(43) by a similar approach as that reported by White [8] in a short communication
without giving experimental details for the various steps of the preparation of 1-(4-
aminophenyl)-1-deoxy-d-ribitol which has not been characterized by chemical and
physical means. We started from N-(4-bromophenyl)benzamide (47) [13] which was
treated with 2 equiv. of BuLi and then with 2,3:4,5-di-O-isopropylidene-d-ribose (48)
[14] to give N-{4-[(1S)-2,3 :4,5-di-O-isopropylidene-d-ribitol-1-C-yl]phenyl}benzena-
mide (49) in 62% yield. Subsequent LiAlH4 treatment in THF resulted in 1-deoxy-
2,3:4,5-di-O-isopropylidene-1-{4-[(phenylmethyl)amino]phenyl}-d-ribitol (50) which
gave, on further reduction with Pd/H2 under debenzylation, 1-(4-aminophenyl)-1-
deoxy-2,3:4,5-di-O-isopropylidene-d-ribitol (43) in 90% yield. The nucleophilic
displacement in the side chain of 25 with 43 proceeded well in THF to give in 62%
yield 1-{4-{{1-[2-amino-7-methyl-4-(1-methylethoxy)pteridin-6-yl]ethyl}amino}phen-
yl}-1-deoxy-2,3:4,5-di-O-isopropylidene-d-ribitol (44). The ribitol moiety could be
deprotected by mild acid treatment with 0.5n HCl at room temperature to give 45,
whereas heating of 44 in 1n HCl afforded full deprotection to 1-{4-{[1-(2-amino-3,4-
dihydro-7-methyl-4-oxopteridin-6-yl)ethyl]amino}phenyl}-1-deoxy-d-ribitol (46) in
78% yield.
Expectedly, all O4-isopropylpterin derivatives showed very similar UV spectra in
MeOH (Table). The pterins 30, 31, 36 – 38, 42, and 45 were further characterized by the
determination of their pKa values [15] to measure the UV absorption of the cation,
neutral form, and monoanion (Table) showing the specific spectral shifts. An
interesting fact is observed in the cations of 30, 31, and 42 which consist of a mixture
of two cation forms showing the normal N(1)-protonated species with the ab-
sorption band at 320nm and the N(8)-protonated form with its long wavelength
band at 384 – 386 nm reflecting the long cross-conjugated p-electron system [16]
(Scheme 4).
The next step in the anticipated methanopterin (1) synthesis was the stereoselective
glycosylation of the terminal OH group of 45 to form an a-glycosidic linkage. Various
trials under different reaction conditions with 2,3,5-tri-O-benzyl-d-ribofuranose-1-
acetate [17] according to Mukaiyama et al. [18 – 25] did not proceed in the expected
manner. We also tried the trichloroacetimidate method according to Schmidt and
Reichrath [26] and synthesized for this purpose from 2,3-O-isopropylidene-5-O-
(monomethoxytrityl)- (53) and 5-O-benzoyl-2,3-O-isopropylidene-d-ribofuranose
(54) the corresponding b-d-configurated 1-(trichloroacetimidates) 55 and 56, respec-
tively (Scheme 5). Unfortunately, glycosylations with these building blocks were again

Helvetica Chimica Acta – Vol. 90 (2007)
1861

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Helvetica Chimica Acta – Vol. 90 (2007)
Table. UV-Absorption Spectra (MeOH) of Pterin Derivatives. Values in parentheses are those of
shoulders.
lmax [nm]
log e
Solvent or pH
pKa
Molecular form
23
24
25
39
40
41
26
27
28
29
35
32
33
34
43
44
36
235
239
236
236
236
237
229
230265
228
228
244
240)(260362
239
032539030 4.404.41
241
246
266
273
271
266
266
266
263
357
358
359
356
357
358
371
4.36
4.33
4.29
46.404.03.95
46.404.03.97
4.00
4.03
3.98
3.92
3.97
3.94
MeOH
MeOH
MeOH
MeOH
MeOH
3.92
4.37
4.16
4.03
MeOH
4.303.96
3.92
4.23
4.24
4.16
MeOH
MeOH
3.91
3.92
372
4.13
4.24
264
265
276
371
371
388
4.46
361
3.97
364
361
320
342
359
321
342
321
4.16
4.11
4.52
MeOH
MeOH
4.10MeOH
9()4.0 3.90MeOH
4.52
(266)
(4.17)
3.97
MeOH
MeOH
(268)
(261)
251
4.52
4.61
(4.27)
4.29
4.46
4.05
4.21
4.46
(4.15)
(4.58)
4.02
3.94
3.93
4.00
3.84
3.93
4.01
3.84
3.95
MeOH
MeOH
À 1
5
(220)
234
251
251
236
1.60
8.53
þ
0
–
þ
276
4.16
(276)
(308)
278
(3.93)
(3.93)
4.18
11
37
38
À 1
1.80
8.700
3
251
(276)
(3.95)
12
–
þ
220)(2503204.44
8()4.01 4.0
4.32
344
3604.42
320
À 2
0.60
219
(238)
254
20840.303
277
273
251
274
4.33
(4.16)
3
4.73
0
8.63
4.403.90 7
3.98
4.05
4.17
3.94
2.62
4.12
–
4.35
11
– –
45
30
31
42
4.01
3.87
À 1
1.80
8.43
–
þ
238
250(276)
251
342
4.35
6
0
359
4.46
3.97
342
357
3.98
342
357
386
341
358
(3.97)
3.97
(4.10)
4.35
11
0
320386
274
(276)
320384
274
(275)
320
275
2.53
2.42
þ
0
–
þ
(232)
3.86
3.93
5
11
8.47
0
251
251
234
251
251
234
251
(3.77)
3.98 2.71
3.87
(3.83)
4.02
3.88
(3.80)
0
5
4.104.13
4.36
4.00
4.104.15
4.36
8.47
8.38
3.94
2.85
11
À 1
–
þ
2.38
0
5
(276)
3.94
11
–
unsuccessful. However, in a model reaction between 55 and O2,O4-bis(trimethylsi-
lyl)thymine (57) under BF3 catalysis, an a,b-d-anomer mixture 58 was obtained.
The terminal component for the synthesis of 1 was synthesized from 2-
hydroxyglutaric acid (59) which gave with 4-nitrobenzyl chloride the bis(4-nitrobenzyl)
a-hydroxyglutarate (60) (Scheme 6). The latter was transformed with 2-cyanoethyl
N,N,N’,N’-tetraisopropylphosphorodiamidite into the corresponding phosphoramidite
61. To establish its reactivity, a phosphoramidite synthesis of 61 with N6-benzoyl-2’,3’-

Helvetica Chimica Acta – Vol. 90 (2007)
1863
Scheme 4
Scheme 5
di-O-isopropylideneadenosine followed by oxidation to the corresponding phospho-
triester 62 was successfully performed.
Experimental Part
General. TLC: precoated cellulose thin-layer sheets F 1440b LS 254 and silica gel thin-layer sheets
F 1500 LS 254 from Schleicher & Schüll. Column chromatography (CC): silica gel 60 from Merck; FC ¼
flash chromatography. M.p.: Büchi apparatus, model Dr. Totteli; no corrections. The pKa measurements
were performed by the spectrophotometric method [15]. UV: Uvikon-820 from Kontron and Lambda-5

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Helvetica Chimica Acta – Vol. 90 (2007)
Scheme 6
spectrometer from Perkin-Elmer; lmax (log e) in nm. 1H-NMR: Bruker WM-250 spectrometer; chemical
shifts d in ppm rel. to SiMe4, coupling constants J in Hz. Elemental analyses were performed in the
Microanalytical Laboratory of Konstanz University.
6-Acetyl-2-amino-7-methylpteridin-4(3H)-one (8) [11]. A soln. of 2,5,6-triamino-pyrimidin-4(3H)-
one dihydrochloride (5 · 2 HCl) [12] (11.0g, 51.4 mmol) in H 2O (400 ml) was neutralized by conc.
ammonia to pH 5, and then pentane-2,3,4-trione (6) [27] (7.0g, 61.3 mmol) in EtOH (75 ml) was added
under stirring. The mixture was heated under reflux for 30min. The formed yellow precipitate was
collected after cooling and purified by reprecipitation from hot 1n NaOH with AcOH to give, after
washing with H2O and EtOH and drying at 1008, 8.2 g (73%) of 8. Yellowish crystal powder. M.p. > 3208.
pKa 1.62, 7.52. UV (pH 4): 240 (4.04), 300 (4.11), 358 (3.97). 1H-NMR (0.5n NaOD): 2.73 (s, AcÀC(6));
2.61 (s, MeÀC(7)).
6-Acetyl-2-(acetylamino)-7-methylpteridin-4(3H)-one (9). A mixture of 8 (2.5 g, 11.4 mmol) and
Ac2O (25 ml) was heated under reflux in an oil bath with stirring for 6 h. After cooling, evaporation, and
treatment of the residue with MeOH, the yellowish solid was recrystallized from AcOH (100 ml) with
charcoal: 2.6 g (71%) of 9 · AcOH. Colorless needles. M.p. > 2008 (dec.). Rf (CHCl3/MeOH 95 :5) 0.72.
UV (MeOH): 240 (sh, 4.08), 303 (4.18), 335 (4.22). 1H-NMR (CDCl3): 12.30(br. s, 1 NH); 12.01 (br. s,
1 NH); 2.76 (s, AcÀC(6)); 2.65 (s, MeÀC(7)); 2.23 (s, AcN). Anal. calc. for C11H11N5O3 · AcOH (321.2):
C 48.59, H 4.70, N 21.80; found: C 48.52, H 4.60, N 22.11.
6-Acetyl-7-methyl-2-[(2-methyl-1-oxopropyl)amino]pteridin-4(3H)-one (10). A suspension of
8
(1.0g, 4.57 mmol) in abs. pyridine (20ml) was treated with isobutyric acid anhydride ( ¼2-methylpro-
panoic acid anhydride; 3.8 ml, 22.6 mmol) and heated under reflux at 130– 140 8 for 12 h. After cooling,
MeOH (10ml) was added, the mixture stirred for 30min and then evaporated, and the residue twice co-
evaporated with AcOEt. The residue was crystallized from hexane/AcOEt 2 :1: 1.06 g (80%) of 10.
Colorless crystals. M.p. 196 – 1978. Rf (CHCl3/MeOH 95 :5) 0.88. 1H-NMR (CDCl3): 12.55 (br. s, 1 NH);
10.00 (br. s, 1 NH); 2.92 (s, AcÀC(6)); 2.85 (m, Me2CH); 2.82 (s, MeÀC(7)); 1.28 (d, Me2CH). Anal.
calc. for C13H15N5O3 (289.3): C 53.97, H 5.23, N 24.21; found: C 54.24, H 5.33, N 24.18.
6-Acetyl-2-[(2,2-dimethyl-1-oxopropyl)amino]-7-methylpteridin-4(3H)-one (11). As described for
10, with 8 (7.0g, 31.9 mmol), pivalic anhydride ( ¼2,2-dimethylpropanoic acid anhydride; 27 ml,
133 mmol), and abs. pyridine (110ml) for 9 h. After cooling, MeOH (50ml) was slowly added with
stirring. Evaporation and treatment with hexane gave 8.62 g (89%) of 11. Colorless crystals. M.p. 1188. Rf

Helvetica Chimica Acta – Vol. 90 (2007)
1865
(CHCl3/MeOH 95 :5) 0.62. 1H-NMR (CDCl3): 12.75 (br. s, 1 NH); 8.80(br. s, 1 NH); 2.94 (s, AcÀC(6));
2.81 (s, MeÀC(7)); 1.36 (d, Me3C). Anal. calc. for C14H17N5O3 (303.3): C 55.44, H 5.65, N 23.09; found: C
55.01, H 5.70, N 22.82.
2-Amino-6-(1-hydroxyethyl)-7-methylpteridin-4(3H)-one (12).
A suspension of 8 (13.0g,
59.3 mmol) in H2O (1.2 l) was heated to 908, and then, under stirring, NaBH4 (7.6 g, 0.2 mol) was
added in small portions. A clear soln. was obtained, and, on cooling, a yellowish precipitate separated.
The mixture was acidified by AcOH to pH 5 – 6, the solid collected, washed with H2O, and then
reprecipitated from hot 1n NaOH/AcOH to give, after drying at 1008, 10.5 g (80%) of 12. Yellowish
1
crystal powder. M.p. > 3508. Rf (cellulose, PrOH/1% aq. NH3 soln. 2 :1) 0.42. H-NMR (0.5n NaOD):
5.35 – 5.15 (m, 1 HÀC(1’)); 2.61 (s, MeÀC(7)); 1.54 (d, Me(2’)). Anal. calc. for C9H11N5O2 · 0.5 H2O
(230.2): C 46.96, H 4.81, N 30.43; found: C 46.88, H 5.20, N 30.51.
2-(Acetylamino)-6-(1-hydroxyethyl)-7-methylpteridin-4(3H)-one (13). To a suspension of 9 (0.82 g,
3.13 mmol) in MeOH (20ml), NaBH 4 (0.38 g, 10 mmol) was added slowly in small portions while
stirring. After consumption of 9 (TLC monitoring), the soln. was evaporated, the residue treated with
10% AcOH, and the solid collected, washed with little H2O, and dried in a vacuum desiccator: 0.625 g
(76%) of 13. Colorless crystal powder. M.p. > 2108 (dec.). Rf (silica gel, CHCl3/MeOH 95 :5) 0.32.
1H-NMR (CDCl3): 12.30(br. s, 1 NH); 12.05 (br. s, 1 NH); 5.15 ((m, HÀC(1’)); 4.70(br. s, OH); 2.76 (s,
MeÀC(7)); 2.21 (s, AcN); 1.61 (d, Me(2’)). Anal. calc. for C11H13N5O3 (263.3): C 50.18, H 4.98, N 26.60;
found: C 49.33, H 5.02, N 26.23.
6-(1-Hydroxyethyl)-7-methyl-2-[(2-methyl-1-oxopropyl)amino]pteridin-4(3H)-one (14). As descri-
bed for 13, with 10 (0.867 g, 3 mmol) in MeOH (20 ml) and NaBH4 (0.38 g, 10 mmol). After evaporation,
the residue was extracted with CHCl3, the extract washed with H2O, dried (Na2SO4), and evaporated,
and the residue dried at 608: 0.685 g (84%) of 14. Colorless crystal powder. M.p. 177 – 1808. Rf (CHCl3/
MeOH 95 :5) 0.38. 1H-NMR (CDCl3): 12.54 (br. s, 1 NH); 9.29 (br. s, 1 NH); 5.16 (m, HÀC(1’)); 4.10(br.
s, OH); 2.75 (m, Me2CH); 2.72 (s, MeÀC(7)); 1.53 (d, Me(2’)); 1.29 (d, Me2CH). Anal. calc. for
C13H17N5O3 (291.3): C 53.60, H 5.88, N 24.04; found: C 55.53, H 5.55, N 23.81.
2-[(2,2-Dimethyl-1-oxopropyl)amino]-6-(1-hydroxyethyl)-7-methylpteridin-4(3H)-one (15). As de-
scribed for 13, with 11 (8.7 g, 28.65 mmol), NaBH4 (3.8 g, 0.1 mol), and MeOH (150 ml). After
evaporation, the residue was extracted with CHCl3, the extract washed with H2O, dried (Na2SO4), and
evaporated, and the residue dried in a vacuum desiccator: 5.95 g (68%) of 15. Colorless crystal powder.
M.p. 119 – 1218. Rf (CHCl3/MeOH 95 :5) 0.65. 1H-NMR (CDCl3): 12.53 (br. s, 1 NH); 9.18 (br. s, 1 NH);
5.15 ((m, HÀC(1’)); 4.50(br. s, OH); 2.73 (s, MeÀC(7)); 1.53 (d, Me(2’)); 1.37 (s, Me3C). Anal. calc. for
C14H19N5O3 (305.3): C 55.07, H 6.27, N 22.94; found: C 54.75, H 6.37, N 22.64.
2-Amino-6-(1-bromoethyl)-7-methylpteridin-4(3H)-one Hydrobromide (16 · HBr). A suspension of
12 (3.5 g, 15.8 mmol) in conc. (48%) HBr soln. (7 ml) was heated under reflux for 10min ( !dark brown
soln.). On cooling, an almost colorless precipitate was obtained. The solid was washed with little EtOH
and Et2O and then recrystallized from conc. HBr soln.: 1.65 g (29%) 16 · HBr. Colorless crystals. M.p.
1
> 3508. H-NMR (CF3COOD): 8.29 (br. s, NH2); 5.57 – 5.37 (q, HÀC(1’)); 2.92 (s, MeÀC(7)); 2.20( d,
Me(2’)). Anal. calc. for C9H10BrN5O · HBr (365.0): C 29.61, H 3.04, N 19.19; found: C 30.10, H 3.00, N
19.06.
6-(1-Bromoethyl)-7-methyl-2-[(2-methyl-1-oxopropyl)amino]pteridin-4(3H)-one (17). A soln. of 14
(0.37 g, 1.27 mmol) in CHCl3 (10ml) was cooled in an ice bath, and then thionyl bromide (0.11 mml,
1.4 mmol) was added under stirring. The mixture was stirred for 15 min at 0– 5 8, then for 1 h at r.t. After
evaporation, the residue was purified by CC (silica gel (10g), CH 2Cl2/MeOH 50:1). The product was
dried in a vacuum desiccator: 0.324 g (72%) of 17. Yellowish powder. M.p. > 1808 (dec.). Rf (CHCl3/
1
MeOH 95 :5) 0.67. UV (MeOH): 203 (4.31), 240 (sh, 4.05), 276 (4.03), 333 (3.81). H-NMR (CDCl3):
12.53 (br. s, 1 NH); 9.22 (br. s, 1 NH); 5.41 (m, HÀC(1’)); 2.85 – 2.75 (m, Me2CH); 2.82 (s, MeÀC(7));
2.22 (d, Me(2’)); 1.32 (d, Me2CH). Anal. calc. for C13H16BrN5O2 (354.2): C 44.08, H 4.55, N 19.77; found:
C 44.19, H 4.71, N 19.01.
6-(1-Bromoethyl)-2-[(2,2-dimethyl-1-oxopropyl)amino]-7-methylpteridin-4(3H)-one (18). As de-
scribed for 17, with 15 (4.4 g, 14.4 mmol) in CH2Cl2 (100 ml) and thionyl bromide (1.34 ml, 17.3 mmol) for
15 min at 0– 5 8 and 2 h at r.t. Purification by CC (silica gel (50g), CH 2Cl2/MeOH 100 :1) gave, after
drying in a vacuum desiccator over KOH, 4.79 g (90%) of 18. Colorless powder. M.p. > 1658 (dec.). Rf

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Helvetica Chimica Acta – Vol. 90 (2007)
1
(CHCl3/MeOH 95 :5) 0.80. UV (MeOH): 203 (4.34), 240 (sh, 4.07), 276 (4.09), 333 (3.83). H-NMR
(CDCl3): 12.30(br. s, 1 NH); 9.45 (br. s, 1 NH); 5.34 (m, HÀC(1’)); 2.84 (s, MeÀC(7)); 2.24 (d, Me(2’));
1.24 (s, Me3C). Anal. calc. for C14H18BrN5O2 (368.2): C 45.66, H 4.93, N 19.12; found: C 45.31, H 4.87, N
18.98.
1-[2-Amino-7-methyl-4-(1-methylethoxy)pteridin-6-yl)ethanone (20). a) A mixture of 6-(1-methyl-
ethoxy)pyrimidine-2,4,5-triamine (19) [12] (10.8 g, 59 mmol) and pentane-2,3,4-trione (6; 10.0 g,
87.6 mmol) in EtOH (300 ml) was heated to 608 for 30min. The mixture was evaporated and the
residue recrystallized from MeOH/H2O: 12.1 g (79%) of 20. Yellowish crystals. M.p. 218 – 2198.
b) A mixture of 6-(1-methylethoxy)-5-nitrosopyrimidine-2,4-diamine (21) [12] (16.1 g, 67.4 mmol)
in pentane-2,4-dione (22; 165 ml) was heated under reflux for 5 h until the educt was consumed. The
mixture was evaporated and the brown residue recrystallized from MeOH/H2O with charcoal: 12.6 g
(72%) of 20. Yellowish crystals. M.p. 2208. Rf (CHCl3/MeOH 95 :5) 0.74. UV (MeOH): 207 (4.25), 252
(4.17), 298 (4.03), 357 (4.11). 1H-NMR (CDCl3): 5.65 (br. s, 2 NH2); 5.56 (m, Me2CH); 2.91 (s,
AcÀC(6)); 2.76 (s, MeÀC(7)); 1.51 (d, Me2CH). Anal. calc. for C12H15N5O2 (262.3): C 55.16, H 5.79, N
26.80; found: C 54.81, H 5.68, N 26.38.
2-Amino-a,7-dimethyl-4-(1-methylethoxy)pteridine-6-methanol (23). To a suspension of 20 in
MeOH (200 ml), NaBH4 was added in small portions under stirring until the educt had disappeared
(TLC monitoring). The soln. was evaporated and the residue dissolved in CHCl3. The extract was
washed with H2O, dried (Na2SO4), and evaporated, and the residue recrystallized from H2O (400 ml):
7.42 g (70%) of 23. Colorless crystals. M.p. 222 – 2238. Rf (CHCl3/MeOH 95 :5) 0.43. 1H-NMR (CDCl3):
5.61 (m, Me2CH); 5.31 (br. s, NH2); 5.12 (m, HÀC(1’)); 4.40( d, OH); 2.71 (s, MeÀC(7)); 1.48 (m,
Me(2’), Me2CH). Anal. calc. for C12H17N5O2 (264.3): C 54.74, H 6.51, N 26.60; found: C 54.70, H 6.46, N
26.37.
6-(1-Chloroethyl)-7-methyl-4-(1-methylethoxy)pteridin-2-amine (24).
A soln. of 23 (7.5 g,
28.5 mmol) in CHCl3 (350ml) was cooled to 0– 5 8, and then thionyl chloride (10.5 ml, 158 mmol) in
CHCl3 (120ml) was added dropwise under stirring. After warming to r.t., the mixture was stirred for 1 h
followed by evaporation. The yellowish residue was purified by CC (silica gel (100 g), CHCl3/MeOH
50:1). The product fractions (2 l) were evaporated: solid 24 (6.55 g, 83%), pure enough for the following
reactions. An anal. sample was obtained by recrystallization from toluene: crystals. M.p. > 2008 (dec.). Rf
(CHCl3/MeOH 95 :5) 0.60. 1H-NMR (CDCl3): 9.55 (br. s, 1 NH); 7.32 (br. s, 1 NH); 5.52 ((m, Me2CH);
5.39 (q, HÀC(1’)); 2.81 (s, MeÀC(7)); 2.03 (d, Me(2’)); 1.48 (m, Me2CH). Anal. calc. for C12H16ClN5O
(281.7): C 51.16, H 5.72, N 24.86; found: C 51.21, H 5.74, N 24.90.
6-(1-Bromoethyl)-7-methyl-4-(1-methylethoxy)pteridin-2-amine (25).
A soln. of 23 (6.2 g,
23.55 mmol) in abs. CHCl3 (250ml) was cooled to 0– 5 8, and then thionyl bromide (5.65 g, 27.1 mmol)
in CHCl3 (20ml) was added dropwise under stirring. After warming to r.t., the mixture was stirred for
another how and then evaporated to a yellowish foam which was purified by CC (silica gel (50g),
CH2Cl2/MeOH 50:1). The product was dried under high vacuum: 6.55 g (85%) of 25, pure enough for
the subsequent reactions. Amorphous solid. M.p. > 1808 (dec.). Rf (CHCl3/MeOH 95 :5) 0.68. 1H-NMR
(CDCl3): 9.36 (br. s, 1 NH); 6.91 (br. s, 1 NH); 5.64 (m, Me2CH); 5.36 (q, HÀC(1’)); 2.76 (s, MeÀC(7));
2.15 (d, Me(2’)); 1.49 (m, Me2CH).
7-Methyl-6-[1-(1-methylethoxy)ethyl]-N4-propylpteridine-2,4-diamine (26). To a soln. of 24 (0.5 g,
1.77 mmol) in iPrOH (20ml) was added propan-1-amine (0.35 ml, 4.3 mmol) and then heated to 80 8 for
24 h. The mixture was evaporated, and the residue purified by CC (silica gel (20g), CHCl 3/MeOH 50:1).
The product was recrystallized from toluene (25 ml): 0.284 g (53%) of 26. Yellow crystals. M.p. 144 –
1458. Rf (CHCl3/MeOH 95 :5) 0.32. 1H-NMR (CDCl3): 6.93 (br. s, NH); 5.06 (br. s, NH2); 4.89 (m,
HÀC(1’)); 3.54 (m, Me2CH, MeCH2CH2N); 2.75 (s, MeÀC(7)); 1.73 (m, MeCH2CH2N); 1.54 (d,
Me(2’)); 1.19 – 107 (m, Me2CH); 1.02 (t, MeCH2CH2N). Anal. calc. for C15H24N6O (304.4): C 59.19, H
7.95, N 27.61; found: C 58.78, H 7.86, N 27.42.
N4-(2,2-Dimethylpropyl)-7-methyl-6-[1-(1-methylethoxy)ethyl]pteridin-2,4-diamine (27). As descri-
i
bed for 26, with 24 (0.5 g, 1.77 mmol), 2,2-dimethylpropan-1-amine (0.5 ml, 4.3 mmol), and PrOH
(20ml) for 14 h under reflux. Purification by CC (silica gel (20g), CHCl 3/MeOH 50:1), followed by
treatment of the product with Et2O, gave 0.355 g (60%) of 27. Yellow powder. M.p. 154 – 1558. Rf (CHCl3/
MeOH 95 :5) 0.47. 1H-NMR (CDCl3); 7.08 (br. s, NH); 5.06 (br. s, NH2); 4.86 (m, CH(1’)); 3.75 – 3.30( m,

Helvetica Chimica Acta – Vol. 90 (2007)
1867
Me2CH, CH2N); 2.74 (s, MeÀC(7)); 1.54 (d, Me(2’)); 1.16 (m, Me2CH); 1.02 (s, Me3C). Anal. calc. for
C17H28N6O (332.5): C 61.42, H 8.49, N 25.28; found: C 61.12, H 8.62, N 25.11.
7-Methyl-6-[1-(1-methylethoxy)ethyl]-N4-(phenylmethyl)pteridine-2,4-diamine (28). As described
for 26, with 24 (0.5 g, 1.77 mmol), benzenemethanamine (0.6 ml, 5.35 mmol), and iPrOH (20ml) for 24 h
at 1008. Purification by CC (silica gel (20g), CHCl 3/MeOH 50:1), followed by treatment of the product
with Et2O, gave 0.36 g (58%) of 28. Yellow crystals. M.p. 137 – 1398. Rf (CHCl3/MeOH 95 :5) 0.26.
1H-NMR (CDCl3): 7.38 (m, Ph); 7.20(br. s, NH); 5.11 (br. s, NH2); 4.84 (m, HÀC(1’), CH2N); 3.55 (m,
Me2CH); 2.78 (s, MeÀC(7)); 1.51 (d, Me(2’)); 1.13 (m, Me2CH). Anal. calc. for C19H24N6O (352.4): C
64.75, H 6.86, N 23.85; found: C 64.66, H 6.75, N 23.84.
N4-(2,2-Dimethylpropyl)-6-(1-ethoxyethyl)-7-methylpteridine-2,4-diamine (29). As described for 26,
with 24 (0.2 g, 0.71 mmol), 2,2-dimethylpropan-1-amine (0.5 ml, 4.3 mmol), and EtOH (20 ml) for 14 h
under reflux. Purification by CC (silica gel (20g), CHCl 3/MeOH 50:1), followed by recrystallization
from toluene (15 ml), gave 0.135 g (60%) of 29. Yellow crystals. M.p. 168 – 1698. Rf (CHCl3/MeOH 95 :5)
0.53. 1H-NMR (CDCl3): 7.01 (br. s, NH); 5.06 (br. s, NH2); 4.78 (m, HÀC(1’)); 3.60– 3.38 ( m, MeCHO2,
CH2N); 2.74 (s, MeÀC(7)); 1.58 (d, Me(2’)); 1.22 (t, MeCH2O); 1.02 (s, Me3C). Anal. calc. for C16H26N6O
(318.4): C 60.35, H 8.23, N 26.39; found: C 60.09, H 8.18, N 26.23.
2-Amino-7-methyl-6-[1-(1-methylethoxy)ethyl]pteridin-4(3H)-one (30). a) A soln. of 7-methyl-4-(1-
methylethoxy)-6-[1-(1-methylethoxy)ethyl]pteridin-2-amine (41; 0.5 g, 1.64 mmol) in 0.2n NaOH
(20ml) and dioxane (10ml) was heated under reflux for 2 h. The warm soln. was acidified by AcOH,
and the precipitate collected after cooling. Washing with H2O and MeOH followed by drying at 1008 gave
0.335 g (75%) of 30. Yellowish powder. M.p. > 3008.
b) A soln. of 0.1 g of 26, 27, or 28 in 1n NaOH (5 ml) and dioxane (5 ml) was heated under reflux for
2 h. The mixture was diluted with H2O (10ml) and the hot soln. acidified by AcOH. The precipitate was
collected after cooling and dried at 1008: 68 – 72 mg (81 – 88%) of 30. Yellowish powder. M.p. > 3008. Rf
(cellulose, PrOH/1% aq. NH3 soln. 2 :1) 0.70. 1H-NMR (0.5n NaOD): 4.84 (m, HÀC(1’)); 3.45 (m,
Me2CH); 2.41 (s, MeÀC(7)); 1.26 (d, Me(2’)); 0.90 (d, Me2CH). Anal. calc. for C12H17N5O2 · 0.5 H2O
(272.3): C 52.93, H 6.66, N 25.72; found: C 52.86, H 6.41, N 25.75.
2-Amino-6-(1-ethoxyethyl)-7-methylpteridin-4(3H)-one (31). a) A soln. of 6-(1-ethoxyethyl)-7-
methyl-4-(1-methylethoxy)pteridin-2-amine (40; 0.2 g, 0.69 mmol) in 0.2n NaOH (10ml) and dioxane
(10ml) was refluxed for 2 h. After concentration to half of the volume, H 2O (20ml) was added and the
mixture heated and then acidified by AcOH. The resulting precipitate was collected after cooling,
washed with H2O and MeOH, and dried at 1008: 0.143 g (83%) of 31. Yellowish powder. M.p. > 2608.
b) Analogous treatment of 29 gave 0.124 g (73%) of 31. Yellowish powder. M.p. > 2608. Rf
(cellulose, PrOH/1% aq. NH3 soln. 2 :1) 0.65. 1H-NMR (0.5n NaOD): 4.73 (m, HÀC(1’)); 3.35 – 3.22 (m,
MeCH2O); 2.38 (s, MeÀC(7)); 1.26 (d, Me(2’)); 0.94 (t, MeCH2O). Anal. calc. for C11H15N5O2 · 0.5 H2O
(258.3): C 51.15, H 6.24, N 27.12; found: C 51.16, H 6.11, N 27.22.
2-Amino-a,7-dimethyl-4-(1-methylethoxy)-N-phenylpteridine-6-methanamine (32). To a soln. of 25
(0.328 g, 1 mmol) in MeCN (15 ml) was added freshly distilled benzenamine (0.146 g, 1.6 mmol), and the
mixture was heated to 608 for 4 h. After evaporation, the residue was treated with H2O and the solid
collected and purified by CC (silica gel (10g), CH 2Cl2/MeOH). The product was recrystallized from
toluene: 0.231 g (68%) of 32. Yellowish crystal powder. M.p. 201 – 2028. Rf (silica gel, CHCl3/MeOH
95 :5) 0.46. 1H-NMR (CDCl3): 7.13 (m, 2 H o to NH); 6.73 (m, 3 arom. H); 5.53 (m, Me2CH); 5.22 (br. s,
NH2); 4.95 (m, HÀC(1’)); 2.77 (s, MeÀC(7)); 1.49 (m, Me(2’), Me2CH). Anal. calc. for C18H22N6O
(338.4): C 63.89, H 6.55, N 24.83; found: C 63.94, H 6.55, N 24.22.
2-Amino-a,7-dimethyl-4-(1-methylethoxy)-N-(4-methylphenyl)pteridine-6-methanamine (33). As
described for 32, with 25 (0.29 g, 0.9 mmol), 4-methylbenzenamine (0.14 g, 1.35 mmol), and DMF
(15 ml) for 1 h: 0.203 g (65%) of 33. Yellowish solid. M.p. > 2108 (dec.). Rf (silica gel, CHCl3/MeOH
95 :5) 0.63. 1H-NMR (CDCl3): 6.96 (m, 2 H o to NH); 6.61 (m, 2 arom. H); 5.52 (m, Me2CH); 5.30(br. s,
NH2); 4.98 (m, HÀC(1’)); 2.75 (s, MeÀC(7)); 2.21 (s, MeC6H4); 1.51 (m, Me(2’), Me2CH). Anal. calc. for
C19H24N6O (352.4): C 64.75, H 6.86, N 23.85; found: C 64.41, H 6.87, N 23.65.
Ethyl 4-{{1-[2-Amino-7-methyl-4-(1-methylethoxy)pteridin-6-yl]ethyl}amino}benzoate (34). As de-
scribed for 32, with 25 (0.328 g, 1 mmol), ethyl 4-aminobenzoate (0.265 g, 1.6 mmol), and DMF (20 ml)
for 3 h: 0.202 g (49%) of 34. Yellowish solid. M.p. > 2208 (dec.). Rf (silica gel, CHCl3/MeOH 95 :5) 0.58.

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Helvetica Chimica Acta – Vol. 90 (2007)
1H-NMR (CDCl3): 7.89 (d, 2 H o to COOEt); 6.67 (d, 2 H o to NH); 5.60(br. d, NH); 5.55 (m, Me2CH);
5.35 (br. s, NH2); 5.03 (m, HÀC(1’)); 4.30( q, MeCH2O); 2.77 (s, MeÀC(7)); 1.51 (m, Me(2’), Me2CH);
1.36 (t, MeCH2O). Anal. calc. for C21H26N6O3 (410.4): C 61.44, H 6.38, N 20.48; found: C 61.41, H 6.35, N
20.10.
7-Methyl-N4-(4-methylphenyl)-6-{1-[(4-methylphenyl)amino]ethyl}pteridine-2,4-amine (35). A soln.
of 24 (0.5 g, 1.77 mmol) and 4-methylbenzenamine (1.5 g, 13.8 mmol) in MeCN (50 ml) was heated to 708
for 18 h. After evaporation, the residue was dissolved in CHCl3, the soln. washed with H2O, dried
(Na2SO4), concentrated and the residue recrystallized from toluene (80ml): 0.416 g (61%) of 35. Yellow
crystals. M.p. 244 – 2458. Rf (silica gel, CHCl3/MeOH 95 :5) 0.65. 1H-NMR (CDCl3): 8.58 (br. s, NH); 7.69
(d, 2 H o to Me); 7.21 (d, 2 H o to Me); 6.96 (d, 2 H o to NH); 6.58 (d, 2 H o to NH); 5.24 (br. s, NH2);
4.97 (m, HÀC(1’)); 2.67 (s, MeÀC(7)); 2.38 (s, MeC6H4); 2.19 (s, MeC6H4); 1.55 (d, Me(2’)). Anal. calc.
for C23H25N7 (399.5): C 69.15, H 6.31, N 24.54; found: C 68.99, H 6.29, N 24.08.
2-Amino-7-methyl-6-[1-(phenylamino)ethyl]pteridin-4(3H)-one (36). A soln. of 32 (0.12 g,
0.35 mmol) in dioxane (10 ml) was treated with 0.1n NaOH (10ml) and heated to 80 8 for 5 h. The
mixture was concentrated to a small volume, diluted with H2O (20ml), heated, and acidified with AcOH.
On cooling, the precipitate was collected and recrystallized from DMF/H2O: 88 mg (84%) of 36. Yellow
powder. M.p. > 3008. Rf (cellulose, PrOH/1% aq. NH3 soln. 2 :1) 0.76. 1H-NMR (CF3COOD): 8.70(br. s,
NH2); 7.64 (m, 5 arom. H); 5.41 (q, HÀC(1’)); 2.80( s, MeÀC(7)); 1.76 (d, Me(2’)). Anal. calc. for
C15H16N6O (296.3): C 60.79, H 5.44, N 28.36; found: C 60.56, H 5.40, N 28.28.
2-Amino-7-methyl-6-{1-[(4-methylphenyl)amino]ethyl}pteridin-4(3H)-one (37). a) A soln. of 33
(0.17 g, 0.48 mmol) in dioxane (15 ml) and 0.1n NaOH (15 ml) was heated under reflux for 5 h. After
evaporation to a small volume, addition of H2O, heating, and acidifying with AcOH, the precipitate was
collected, washed with H2O, and dried at 1008: 0.142 g (90%) of 37. Yellow powder. M.p. > 3008.
b) Analogously to procedure a), with 35 (0.2 g, 0.5 mmol): 0.135 g (82%) of 37. Yellow powder. M.p.
> 3008. Rf (cellulose, PrOH/1% aq. NH3 soln. 2 :1) 0.84. 1H-NMR (0.5n NaOD): 6.70( d, 2 H o to NH);
6.50( d, 2 H o to Me); 4.67 (m, HÀC(1’)); 2.38 (s, MeÀC(7)); 1.85 (s, MeC6H4); 1.20( s, Me(2’)). Anal.
calc. for C16H18N6O · H2O (328.4): C 58.53, H 6.14, N 25.59; found: C 58.75, H 5.89, N 25.23.
Ethyl 4-{[1-(2-Amino-3,4-dihydro-7-methyl-4-oxopteridin-6-yl)ethyl]amino}benzoate (38). As de-
scribed for 37, with 34 (0.2 g, 0.48 mmol), 0.1n NaOH (20ml), and dioxane (20ml) for 4 h: 0.155 g (89%)
1
of 38. Yellowish powder. M.p. > 3008. Rf (cellulose, PrOH/1% aq. NH3 soln. 2 :1) 0.27. H-NMR (0.5n
NaOD): 6.70( d, 2 H o to COOH); 6.63 (d, 2 H o to NH); 4.68 (m, HÀC(1’)); 2.43 (s, MeÀC(7)); 1.23 (s,
Me(2’)). Anal. calc. for C16H16N6O3 · H2O (358.3): C 53.62, H 4.85, N 23.45; found: C 53.35, H 5.06, N
23.12.
6-(1-Methoxyethyl)-7-methyl-4-(1-methylethoxy)pteridin-2-amine (39). To a soln. of 24 (0.5 g,
1.77 mmol) in abs. MeOH (10ml) was added Et 3N (1 ml) and then heated under reflux for 2 h. The
insoluble solid was filtered off and the filtrate concentrated. The residue was treated with H2O (20ml) to
form a microcrystalline material which was dried and then recrystallized from toluene: 0.295 g (60%) of
1
39. Colorless crystals. M.p. 216 – 2178. Rf (silica gel, CHCl3/MeOH 95 :5) 0.75. H-NMR (CDCl3): 5.52
(m, Me2CH); 5.31 (br. s, NH2); 4.74 (q, HÀC(1’)); 3.29 (s, MeO); 2.75 (s, MeÀC(7)); 1.56 (s, Me(2’));
1.46 (m, Me2CH). Anal. calc. for C13H19N5O2 (277.3): C 56.30, H 6.91, N 25.25; found: C 55.99, H 6.85, N
25.43.
6-(1-Ethoxyethyl)-7-methyl-4-(1-methylethoxy)pteridin-2-amine (40). As described for 39, with 24
(0.5 g, 1.77 mmol), Et3N (1 ml), and abs. EtOH (10ml): 0.28 g (54%) of 40. Colorless crystals. M.p. 207 –
2088. Rf (silica gel, CHCl3/MeOH 95 :5) 0.48. 1H-NMR (CDCl3): 5.56 (m, Me2CH); 5.30(br. s, NH2); 4.82
(q, HÀC(1’)); 3.51 – 3.34 (m, MeCH2O); 2.77 (s, MeÀC(7)); 1.57 (s, Me(2’)); 1.46 (m, Me2CH); 1.18 (t,
MeCH2O). Anal. calc. for C14H21N5O2 (291.4): C 57.71, H 7.26, N 24.04; found: C 57.92, H 7.13, N 24.19.
7-Methyl-4-(1-methylethoxy)-6-[1-(1-methylethoxy)ethyl]pteridin-2-amine (41). A soln. of 24
i
(0.28 g, 1 mmol) and Et3N (0.8 ml) in abs. PrOH (20ml) was heated under reflux for 6 h. After
evaporation, the residue was treated with H2O, and the crystals were collected and purified by CC (silica
gel (30g), CH 2Cl2/MeOH 50 :1). The product was recrystallized from toluene (30 ml): 0.182 g (60%) of
41. Colorless crystals. M.p. 200 – 2028. Rf (silica gel, CHCl3/MeOH 95 :5) 0.51. 1H-NMR (CDCl3): 5.56 (m,
Me2CH); 5.20(br. s, NH2); 4.95 (q, HÀC(1’)); 3.57 (m, Me2CH); 2.83 (s, MeÀC(7)); 1.62 (s, Me(2’)); 1.48

Helvetica Chimica Acta – Vol. 90 (2007)
1869
(m, Me2CH); 1.18 (m, Me2CH). Anal. calc. for C15H23N5O2 (305.4): C 59.00, H 7.59, N 22.93; found: C
59.02, H 7.50, N 22.72.
2-Amino-6-(1-methoxyethyl)-7-methylpteridin-4(3H)-one (42). A soln. of 39 (0.15 g, 1.54 mmol) in
0.2n NaOH (10ml) and dioxane (15 ml) was heated under reflux for 2 h. The mixture was concentrated
to a small volume, then diluted with H2O (20ml), heated, and acidified with AcOH. The precipitate was
collected after cooling, washed with H2O and MeOH, and dried at 1008: 0.102 g (80%) of 42. Yellow
powder. M.p. > 2608. Rf (cellulose, PrOH/1% aq. NH3 soln. 2 :1) 0.56. 1H-NMR (0.5n NaOD): 4.63 (m,
HÀC(1’)); 3.06 (s, MeO); 2.36 (s, MeÀC(7)); 1.26 (d, Me(2’)). Anal. calc. for C11H15N5O2 · 0.25 H2O
(239.8): C 50.10, H 5.68, N 29.21; found: C 50.45, H 5.57, N 28.94.
1-(4-Aminophenyl)-1-deoxy-2,3 :4,5-di-O-isopropylidene-d-ribitol (43). A soln. of 1-deoxy-2,3:4,5-
di-O-isopropylidene-1-{4-[(phenylmethyl)amino]phenyl}-d-ribitol (50; 0.5 g, 1.26 mmol) in EtOH
(30 ml) was treated with 10% Pd/C (0.1 g) under H2 in a shaking apparatus until the H2 uptake ceased
(2 h). The catalyst was filtered off and washed with EtOH, the combined filtrate evaporated, the
obtained syrup dissolved in acetone, and hexane was slowly added until crystallization took place. The
colorless crystals were dried in a vacuum desiccator: 0.348 g (90%) of 43. M.p. 102 – 1048. Rf (silica gel,
hexane/AcOEt 1:1) 0.51. 1H-NMR (CDCl3): 7.10( d, 2 H o to ribitol); 6.63 (d, 2 H o to NH); 4.39 – 390
(m, HÀC(2), HÀC(3), HÀC(4), CH2(5)); 3.40(br. s, NH2); 3.01 – 2.68 (dd, CH2(1)); 1.44 (s, 1 Me); 1.41
(s, 1 Me); 1.37 (s, 1 Me); 1.29 (s, 1 Me). Anal. calc. for C17H25NO4 (307.4): C 66.42, H 8.20, N 4.56; found:
C 66.24, H 8.28, N 4.45.
1-{4-{{1-[2-Amino-7-methyl-4-(1-methylethoxy)pteridin-6-yl]ethyl}amino}phenyl}-1-deoxy-2,3:4,5-
di-O-isopropylidene-d-ribitol (44). To a soln. of 25 (0.2 g, 0.61 mmol) in abs. THF (5 ml) was added 43
(0.282 g, 0.91 mmol), and then the mixture was stirred at r.t. overnight (18 h). The mixture was
evaporated and the residue purified by CC (silica gel (10g), CH 2Cl2/MeOH 50:1). The product was
dried under high vacuum at 408: 0.21 g (62%) of 44. Yellowish powder. M.p. > 1808 (dec.). Rf (silica gel,
CHCl3/MeOH 95 :5) 0.67). 1H-NMR (CDCl3): 7.10( d, 2 H o to ribitol); 6.66 (d, 2 H o to NH); 5.51 (m,
Me2CH); 5.25 (br. s, NH2); 4.97 (m, MeCHÀC(6’)); 4.40– 3.88 ( m, HÀC(2), HÀC(3), HÀC(4),
CH2(5)); 2.95 (dd, 1 HÀC(1)); 2.76 (s, Me(7)); 2.70( m, 1 HÀC(1)); 1.52 (m, MeCHÀC(6’), Me2CH);
1.44 (s, 1 Me); 1.40( s, 1 Me); 1.36 (s, 1 Me); 1.29 (s, 1 Me). Anal. calc. for C29H40N6O5 (552.7): C 63.02, H
7.30, N 15.21; found: C 63.20, H 7.32, N 14.64.
1-{4-{{1-[2-Amino-7-methyl-4-(1-methylethoxy)pteridin-6-yl]ethyl}amino}phenyl}-1-deoxy-d-ribitol
(45). To a soln. of 44 (0.4 g, 0.72 mmol) in dioxane (4 ml) was added 0.5n HCl (4 ml), and then the
mixture was stirred at r.t. for 3 h. After neutralization with sat. NaHCO3 soln., the mixture was extracted
several times with AcOEt, the combined org. phase evaporated, and the resulting solid purified by FC
(silica gel (Baker), CH2Cl2/MeOH 9 :1 ! 4 :1). The product was dried under high vacuum: 0.19 g (55%)
of 45. Yellowish powder. M.p. > 2008 (dec.). Rf (silica gel, CH2Cl2/MeOH 9 :1) 0.12. 1H-NMR
((D6)DMSO): 7.04 (br. s, NH2); 6.91 (d, 2 H o to ribitol); 6.54 (d, 2 H o to NH); 5.66 (br. s,
NHÀCHÀC(6’)); 5.48 (m, Me2CH); 4.87 (m, NHCHÀC(6’)); 4.60– 4.30 ( m, 4 OH); 3.68 – 3.30( m,
HÀC(2), HÀC(3), HÀ(4), CH2(5)); 2.75 (dd, 1 HÀC(1)); 2.60( s, MeÀC(7)); 2.40( m, 1 HÀC(1)); 1.46
(d, MeCHÀC(6’)); 1.41 (d, Me2CH). Anal. calc. for C23H32N6O5 (472.6): C 58.46, H 6.83, N 17.78; found:
C 48.30, H 6.26, N 17.51.
1-{4-{[1-(2-Amino-3,4-dihydro-7-methyl-4-oxopteridin-6-yl)ethyl]amino}phenyl}-1-deoxy-d-ribitol
(46). To a soln. of 44 (0.12 g, 0.22 mmol) in dioxane (10 ml) was added 1n HCl (10ml), and then the
mixture was heated to 1008 with stirring for 3.5 h. The mixture was evaporated to a small volume and then
neutralized with dil. NaHCO3 soln. The precipitate was collected, washed with H2O and MeOH, and
dried under high vacuum at 408: 76 mg (78%) of 46. Yellowish powder. M.p. > 2608 (dec.). Rf (cellulose,
1
PrOH/1% aq. NH3 soln. 2 :1) 0.41. H-NMR (0.5n NaOD): 6.89 (d, 2 H o to ribitol); 6.66 (d, 2 H o to
NH); NHÀCHÀC(6’) and OÀCH covered by HDO; 4.87 (m, MeCHÀC(6’)); 3.70– 3.38 ( m, HÀC(2),
HÀC(3), HÀC(4’), CH2(5)); 2.75 – 2.27 (m, CH2(1)); 2.49 (s, Me(7)); 1.32 (d, MeCHÀC(6’)). Anal. calc.
for C20H26N6O5 · H2O (430.5): C 53.56, H 6.29, N 18.74; found: C 53.28, H 6.27, N 18.47.
N-4-(Bromophenyl)benzamide (47) [13]. A soln. of 4-bromobenzenamine (20g, 0.116 mmol) in
pyridine (100 ml) was cooled to 0 – 58, and then benzoyl chloride (14.5 ml) was added dropwise under
stirring. The mixture was stirred at r.t. for 30min, and then H 2O was added gradually whereby a
precipitate separated. The solid was collected, washed with H2O, and recrystallized from EtOH (800 ml)

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Helvetica Chimica Acta – Vol. 90 (2007)
with charcoal: 25.5 g (81%) of 47. Colorless crystals. M.p. 200 – 2018 ([13]: 200 – 2028). Rf (silica gel,
hexane/AcOEt 2 :1) 0.55. 1H-NMR ((D6)DMSO): 9.30(br. s, BzNH); 7.45 – 7.12 (m, 9 arom. H).
N-{4-[(1S)-2,3 :4,5-di-O-isopropylidene-d-ribitol-1-C-yl]phenyl}benzenamide (49). A soln. of 47
(3.7 g, 13.7 mmol) in abs. THF (200 ml) was cooled to À 608, and then 1.6m BuLi in hexane (17.1 ml) was
slowly added under stirring, followed by 2,3:4,5-di-O-isopropylidene-d-ribose (48) [14] (2.0g,
8.7 mmol). The mixture was stirred for 15 min at À 608 and then warmed to r.t. within 90min.
Subsequently, Et2O (200 ml) and H2O (100 ml) were added. The org. phase was washed with H2O, dried
(Na2SO4), and concentrated, and the residue purified by CC (silica gel (140g), hexane/AcOEt 4 :1
(! by-products), then hexane/AcOEt 2 :1): 2.32 g (62%) of 49. Solid. M.p. 136 – 1378. Rf (silica gel,
cyclohexane/AcOEt 2 :1) 0.23. 1H-NMR (CDCl3): 7.99 – 7.28 (m, 9 arom. H, NH); 5.08 (dd, 1 HÀC(1’));
4.66 – 3.78 (m, HÀC(2), HÀC(3), HÀC(4’), CH2(5’)); 2.91 (d, OH); 1.52 (s, 1 Me); 1.40( s, 1 Me); 1.35 (s,
2 Me). Anal. calc. for C24H29NO6 (427.5): C 67.43, H 6.84, N 3.28; found: C 66.83, H 6.90, N 3.25.
1-Deoxy-2,3:4,5-di-O-isopropylidene-1-{4-[(phenylmethyl)amino]phenyl}-d-ribitol (50). A soln. of
49 (0.5 g, 1.18 mmol) in abs. THF (40 ml) was treated with LiAlH4 (0.8 g, 21.2 mmol) in a glass autoclave
at 808 for 30h. H 2O was slowly added to the mixture until H2 evolution ceased. The Al(OH)3 was filtered
off and washed with Et2O, and the combined org. phase dried (Na2SO4) and concentrated to give an oil
which crystallized on standing: 0.352 g (75%) of 50. Colorless crystal powder. M.p. 97 – 988. Rf (silica gel,
cyclohexane/AcOEt 2 :1) 0.20. 1H-NMR (CDCl3): 7.37 – 7.26 (m, 5 arom. H); 7.11 (d, 2 H o to NH); 6.59
(d, 2 H o to NH); 4.36 – 3.91 (m, HÀC(2), HÀC(3), HÀC(4), CH2(5)); 4.31 (d, PhCH2); 2.99 – 2.68
(2dd, 2 HÀC(1)); 1.44 (s, 1 Me); 1.42 (s, 1 Me); 1.37 (s, 1 Me); 1.29 (s, 1 Me). Anal. calc. for C24H31NO4
(397.5): C 72.52, H 7.86, N 3.52; found: C 72.69, H 8.10, N 3.53.
1-Deoxy-1-{4-[(phenylmethyl)amino]phenyl}-d-ribitol (51). A soln. of 50 (0.7 g, 1.76 mmol) in 1n
HCl (50ml) was stirred at 100 8 for 1 h. After cooling, the mixture was filtered and the filtrate neutralized
with solid K2CO3. Then the soln. was brought to pH 12 with 1n NaOH followed by extraction with
AcOEt (2 ꢀ 100 ml). The extract was dried (Na2SO4) and concentrated, the residue dissolved in little
acetone, and hexane added slowly until turbidity. After standing in the icebox for several hours, the solid
was collected and dried in a vacuum desiccator: 0.463 g (83%) of 50. Crystal powder. M.p. 129 – 1308. Rf
(silica gel, CHCl3/MeOH 1:1) 0.82. 1H-NMR ((D6)DMSO): 7.36 – 7.19 (m, PhCH2); 6.88 (d, 2 H o to NH,
2 H o to ribitol); 5.99 (t, NH); 4.59 (d, 1 OH); 4.54 (d, 1 OH); 4.35 (m, 2 OH); 4.31 (d, PhCH2); 3.60–
3.25 (m, 3 CH, 1 CH2); 2.72 – 2.32 (2dd, 2 HÀC(1)). Anal. calc. for C18H23NO4 (317.4): C 68.11, H 7.30, N
4.41; found: C 68.18, H 7.35, N 4.54.
1-(4-Aminophenyl)-1-deoxy-d-ribitol (52). a) A mixture of 43 (0.2 g, 0.66 mmol) in dioxane (10 ml)
and 1n HCl (10ml) was refluxed for 3 h. After cooling, the mixture was evaporated, the residue dissolved
in H2O, and the soln. adjusted to pH 11 with 1n NaOH. The soln. was adsorbed on silica gel (10g) and
subjected to CC (silica gel, CHCl3/MeOH 1:1). The product was dried under high vacuum: 0.102 g (69%)
of 52.
b) To a suspension of 51 (0.2 g, 0.62 mmol) in EtOH (50 ml, 96%) was added 10% Pd/C (0.1 g), and
the mixture was hydrogenated under H2 in a shaking apparatus. The consumption of H2 ceased after 1 h.
The catalyst was filtered off through silica gel, the filtrate evaporated, and the resulting syrup crystallized
from acetone/hexane: 0.116 g (81%) of 52. Rf (silica gel, CHCl3/MeOH 1 :1) 0.59. 1H-NMR
((D6)DMSO): 6.87 (d, 2 H o to ribitol); 6.43 (d, 2 H o to NH); 4.76 (br. s, NH2); 4.62 (d, 1 OH); 4.55
(t, OHÀC(5)); 4.38 (m, 2 OH); 3.65 – 3.25 (m, 3 CH, 1 CH2); 2.73 – 2.28 (m, 2 HÀC(1)). Anal. calc. for
C11H17NO4 (227.3): C 58.13, H 7.54, N 6.16; found: C 58.55, H 7.28, N 6.08.
2,3-O-Isopropylidene-5-O-(monomethoxytrityl)-d-ribofuranose (53). A soln. of 2,3-O-isopropyli-
dene-d-ribofuranose [28] (4.2 g, 22.1 mmol) in abs. pyridine (10ml) was treated with monomethoxytrityl
chloride (8.2 g, 26.5 mmol) by stirring at r.t. overnight. After evaporation, dil. NaHCO3 soln. was added,
and the mixture several times extracted with Et2O. The extract was dried (Na2SO4) and again evaporated,
and the residue purified by CC (silica gel (100 g), hexane/AcOEt 9 :1 ! 6 :1). The product was dried
under high vacuum: 8.62 g (84%) of 53. Amorphous solid. Rf (silica gel, hexane/AcOEt 4 :1) 0.51.
1H-NMR (CDCl3): 7.41 – 7.23 (m, 12 arom H); 6.85 (m, 2 H o to MeO); 5.33 (d, HÀC(1)); 4.80( d, OH);
4.67 (d, HÀC(2)); 4.33 (ꢁtꢂ, HÀC(3)); 4.08 (d, HÀC(4)); 3.80( s, MeO); 3.36 (m, 2 HÀC(5)); 1.48 (s,
1 Me); 1.35 (s, 1 Me). Anal. calc. for C28H30O6 (462.5): C 72.71, H 6.54; found: C 72.75, H 6.64.

Helvetica Chimica Acta – Vol. 90 (2007)
1871
2,3-O-Isopropylidene-d-ribofuranose 5-Benzoate (54) [29]. A soln. of 2,3-O-isopropylidene-d-
ribofuranose [28] (2.1 g, 11 mmol) were co-evaporated in abs. pyridine (5 ml) to remove any moisture.
The resulting syrup was dissolved in abs. pyridine (10ml) and cooled in ice. Then benzoyl chloride (1.72 g,
12.1 mmol) was added dropwise with stirring followed by warming to r.t. After 30min, the mixture was
poured on ice and extracted several times with Et2O. The extract was dried (Na2SO4) and concentrated,
and the residue purified by CC (silica gel (50g), hexane/AcOEt 5 :1 ! 4 :1). The product was dried
under high vacuum: 2.87 g (88%) of 54. Colorless oil. Rf (silica gel, hexane/AcOEt 2 :1) 0.59. 1H-NMR
(CDCl3): 8.03 (m, 2 H o to CO); 7.56 – 7.38 (m, 3 arom H); 5.52 (d, HÀC(1)); 4.80( d, HÀC(3)); 4.67 (d,
HÀC(2)); 4.52 (m, 2 HÀC(5)); 4.35 (d, HÀC(4)); 3.55 (d, OH); 1.47 (s, 1 Me); 1.34 (s, 1 Me).
2,3-O-Isopropylidene-5-(monomethoxytrityl)-b-d-ribofuranose 1-(1,1,1-Trichloroethanimidate) (55).
To a soln. of 53 (3.0g, 6.5 mmol) in CH 2Cl2 (10ml) was added 1,1,1-trichloroacetonitrile (3.87 g,
26.7 mmol), followed by a small amount of NaH (10mg) to start the reaction. After stirring for 30min,
more NaH (0.2 g) was added, and the mixture was stirred at r.t. for 4 h. Insoluble material was filtered off,
and the filtrate was evaporated. The residue was purified by CC (silica gel (80g), hexane/AcOEt 7:1 !
5.5 :1). The product was dried under high vacuum: 3.11 g (79%) of 55. Amorphous solid. Rf (silica gel,
hexane/AcOEt 4 :1) 0.66. 1H-NMR (CDCl3): 8.42 (s, NH); 7.44 – 7.20( m, 12 arom. H); 6.80( m, 2 H o to
MeO); 6.22 (d, HÀC(1)); 4.71 (m, 2 HÀC(5)); 4.61 (d, HÀC(2)); 3.79 (s, MeO); 3.40( dd, HÀC(3));
3.09 (ꢁtꢂ, HÀC(4)); 1.53 (s, Me); 1.34 (s, Me). Anal. calc. for C30H30Cl3NO6 (406.9): C 59.37, H 4.98, N
2.31; found: C 59.47, H 5.18, N 2.32.
2,3-O-Isopropylidene-b-d-ribofuranose 5-Benzoate 1-(1,1,1-Trichloroethanimidate) (56). As descri-
bed for 55, with 54 [29] (0.8 g, 2.72 mmol), CH2Cl2 (10ml), and NaH (0.5 g; 1 batch). Purification by CC
(silica gel (10g), CH 2Cl2/Et2O) gave 1.08 g (91%) of 56. Amorphous solid. M.p. 1308. Rf (silica gel,
hexane/AcOEt 4 :1) 0.62. 1H-NMR (CDCl3): 8.55 (s, NH); 8.03 (m, 2 H o to CO); 7.55 – 7.41 (m, 3 arom.
H); 6.37 (d, HÀC(1)); 4.93 (d, HÀC(3)); 4.87 (d, HÀC(2)); 4.61 (d, HÀC(4)); 4.40( m, 2 HÀC(5)); 1.52
(s, 1 Me); 1.35 (s, 1 Me). Anal. calc. for C17H18Cl3NO6 (438.7): C 46.55, H 4.14, N 3.19; found: C 46.82, H
4.26, N 3.37.
2’,3’-O-Isopropylidene-5-methyl-5’-O-(monomethoxytrityl)uridine (58). A mixture of thymine
(0.51 g, 4 mmol) in hexamethyldisilazane (HMDS; 5 ml) and (NH4)2SO4 (20mg) was heated under
reflux overnight to form 5-methyl-2,4-bis[(trimethylsilyl)oxy]pyrimidine (57). The mixture was
evaporated under high vacuum and the residue combined with a soln. of 55 (2.4 g, 4 mmol) in CH2Cl2
(20ml). Then BF 3 · Et2O (0.16 ml, 1.28 mmol) was added under stirring, and the mixture was stirred at r.t.
for 5 h. The mixture was treated with sat. NaHCO3 soln. and then extracted several times with AcOEt,
the org. phase dried (Na2SO4) and concentrated, and the oil purified by FC (silica gel (30g), CH 2Cl2/
MeOH 9 :1). The product was dried under high vacuum: 1.05 (46%) of 58. Amorphous solid consisting of
an a/b-d-anomer mixture. Rf (silica gel, hexane/AcOEt 2 :1) 0.21. UV (MeOH): 230, (sh, 4.28), 266
1
(4.08). H-NMR (CDCl3): 8.28 (s, NH(3)); 7.41 – 7.22 (m, 12 arom. H, HÀC(6)); 6.83 (m, 2 arom. H);
6.50( d, HÀC(1’)); 4.96 (d, HÀC(3’)); 4.56 (dd, HÀC(2’)); 4.40( m, HÀC(4’)); 3.98 (s, MeO); 3.49 (dd,
1 HÀC(5’)); 3.10( dd, 1 HÀC(5’)); 1.93 (s, MeÀC(5)); 1.40( s, Me); 1.26 (s, Me). Anal. calc. for
C33H34N2O7 (570.6): C 69.46, H 6.01, N 4.91; found: C 69.00, H 6.16, N 4.54.
2-Hydroxypentanedioic Acid (59) Disodium Salt [30]. A soln. of l-glutamic acid (75 g, 0.5 mol) in
37.5% H2SO4 soln. (150ml) was cooled to À 108, and then a soln. of KNO2 (85 g, 1 mol) in H2O (150ml)
was added dropwise slowly with stirring. After addition, the soln. was concentrated to 200 ml at < 408.
The precipitating K2SO4 was filtered off and the filtrate continuously extracted with Et2O for 20h. The
extract was evaporated and the residue treated with 1n NaOH (100 ml). After evaporation and co-
evaporation with EtOH, a colorless powder was obtained which was dried in a vacuum desiccator over
P4O10: 60.5 g (62%) of the disodium salt of 59. 1H-NMR (D2O): 3.86 (dd, HÀC(2)); 2.11 (m, CH2(4));
1.86 – 1.66 (m, CH2(3)). Anal. calc. for C5H6Na2O5 (192.1): C 31.24, H 3.14; found: C 30.60, H 3.18.
Bis(4-nitrobenzyl) 2-Hydroxypentanedioate (60). A suspension of the disodium salt of 59 (10g,
52 mmol) and 4-nitrobenzyl chloride (19.7 g, 0.115 mol) in DMF (10 ml) was stirred in at 1208 for 6 h.
The hot soln. was filtered, the filtrate concentrated, and the residue dissolved in excess of AcOEt. After
washing with H2O, drying (Na2SO4), and evaporation, the resulting solid was recrystallized from toluene:
1
16.7 g (77%) of 60. Colorless crystals. M.p. 89 – 908. Rf (silica gel, hexane/AcOEt 1:1) 0.64. H-NMR
(CDCl3): 8.22 (m, 4 H o to NO2); 7.49 (m, 4 H m to NO2); 5.28 (dd, CH2O); 5.19 (s, CH2O); 4.30( m,

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Helvetica Chimica Acta – Vol. 90 (2007)
HÀC(2)); 2.56 (m, CH2(4)); 2.50– 2.32 ( m, CH2(3)); 1.56 (br. s, OH). Anal. calc. for C19H18N2O9 (418.4):
C 54.55, H 4.34, N 6.70; found: C 55.03, H 4.48, N 6.55.
Bis(4-nitrobenzyl) 2-{[(2-Cyanoethoxy)(diisopropylamino)phosphino]oxy}pentanedioate (61). To a
soln. of 60 (0.42 g, 1 mmol) in CH2Cl2 (10ml) was added 2-cyanoethyl N,N,N’,N’-tetraisopropylphos-
phorodiamidite (0.47 g, 1.55 mmol). After 5 min stirring, 1H-tetrazole (0.28 g, 4 mmol) was added for
activation, and the mixture was stirred at r.t. overnight. The mixture was diluted with CHCl3, washed with
phosphate buffer pH 7 and then H2O, the org. phase dried (Na2SO4) and concentrated, and the residue
purified by CC (silica gel (20g), hexane/AcOEt 4 :1 ! 2.5 :1 containing a few drops of Et3N). The
product was dried under high vacuum: 0.53 g (85%) of 61. Colorless amorphous solid. Rf (silica gel,
hexane/AcOEt 2 :1) 0.50. 1H-NMR (CDCl3): 8.21 (m, 4 H o to NO2); 7.51 (m, 4 H m to NO2); 5.25 (dd,
CH2O); 5.18 (s, CH2O); 4.50– 4.32 ( m, HÀC(2)); 3.89 – 3.52 (m, NCCH2CH2, 2 Me2CH); 2.59 (m,
NCCH2CH2, CH2(4)); 2.16 (m, CH2(3)); 1.12 (m, 2 Me2CH). Anal. calc. for C28H35N4O10P (618.6): C
54.37, H 5.70, N 9.06; found: C 53.70, H 5.70, N 9.00.
Bis(4-nitrobenzyl) 2-{[(N6-Benzoyl-2’,3’-O-isopropylideneadenosin-5’-O-yl)(2-cyanoethoxy)phos-
phinyl]oxy}pentanedioate (62). N6-Benzoyl-2’,3’-O-isopropylideneadenosine [31] (92 mg, 0.22 mmol)
was dried under high vacuum overnight and then dissolved under Ar in MeCN (3 ml). To this soln., 61
(0.2 g, 0.32 mmol) and then 1H-tetrazole (70mg, 1 mmol) were added. After stirring for 2 h, a soln. of I 2
(0.5 g) in CH2Cl2/H2O/pyridine 1:1.3 was added dropwise until decoloration ceased. The mixture was
diluted with CHCl3 and washed with sat. NaCl soln. containing some Na2S2O3. The aq. solns. were
reextracted with CHCl3. The combined org. phase was dried (Na2SO4) and evaporated, and the resulting
residue purified by FC (silica gel (10g), CH 2Cl2/MeOH 49 :1). The product was dried under high
vacuum: 0.136 g (66%) of 62. Amorphous solid. Rf (silica gel, CH2Cl2/MeOH 97:3) 0.24. UV (MeOH):
270(4.53). 1H-NMR (CDCl3): 9.09 (br. s, NH); 8.77 (d, HÀC(8) (ado)); 8.15 (m, 4 H o to NO2, HÀC(2)
(ado)); 7.51 (m, 9 arom. H); 6.17 (t-like, HÀC(1’)); 5.43 (m, HÀC(2’)); 5.22 (s, CH2O); 5.14 (s, CH2O,
HÀC(3’)); 4.90( m, HÀC(2)); 4.43 (m, HÀC(4’)); 4.41 – 4.06 (m, CH2(5’), NCCH2CH2); 2.68 (m,
CH2(4)); 2.50( m, NCCH2CH2); 2.29 – 2.04 (m, CH2(3); 1.60(s, 1 Me); 1.37 (s, 1 Me). 31P-NMR(CHCl3):
À 1.58; À 1.64.
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Received May 23, 2007