Pteridines CXX.1 synthesis and properties of tetrahydro-pterins coupled to 1,4-dihydropyridines

Article abstract of DOI:10.3987/COM-08-S(F)70

N²-Isobutyroyl-5,6,7,8-tetrahydropterins (610) have been coupled with nicotinic acid to form the N⁵-nicotinoyl derivatives 1115. Quaternization at the pyridine moiety led to 1931 which can be reduced to the corresponding N-substitute

Full text of DOI:10.3987/COM-08-S(F)70

HETEROCYCLES, Vol. 77, No. 2, 2009
953
HETEROCYCLES, Vol. 77, No. 2, 2009, pp. 953 - 970. © The Japan Institute of Heterocyclic Chemistry
Received, 28th July, 2008, Accepted, 18th September, 2008 Published online, 22nd September, 2008
DOI: 10.3987/COM-08-S(F)70
PTERIDINES CXX.1 SYNTHESIS AND PROPERTIES OF
TETRAHYDRO- PTERINS COUPLED TO 1,4-DIHYDROPYRIDINES
Joachim Rehse and Wolfgang Pfleiderer*
Department of Chemistry, University of Konstanz, D-78457 Konstanz, Germany
E-mail: Wolfgang.pfleiderer@uni-konstanz.de
Dedicated to Professor Emeritus Keiichiro Fukumoto on the occasion of his
75th birthday
Abstract - N2-Isobutyroyl-5,6,7,8-tetrahydropterins (6-10) have been coupled
with nicotinic acid to form the N5-nicotinoyl derivatives 11-15. Quaternization at
the pyridine moiety led to 19-31 which can be reduced to the corresponding
N-substituted 1,4-dihydropyridine dertivatives 35-39. Partial deacylation of the
isobutyroyl group afforded the various types of terahydropterins 16-18, 32-34 and
40-42. The newly synthesized 5,6,7,8-tetrahydropterin derivatives have been
characterized by pKa-determinations, UV- and NMR-spectra as well as elemental
analyses.
INTRODUCTION
Tetrahydrobiopterin (BH4) is an important cofactor for some aromatic monooxygenases which participate
in the synthesis of tyrosine, L-Dopa and 5-hydroxytryptophan. A lack of this cofactor causes several
neurological diseases such as Parkinson disease and atypical phenylketonuria. Since the potential clinical
agent, tetrahydrobiopterin, does not penetrate the blood-brain-barrier very effectively2 this problem may
be overcome by addition of a lipophilic substituent3-5 or by the attachment of a carrier moiety.6,7 The
Bodor-system8-10 offers with the dihydropyridine
pyridinium salt carrier an interesting alternative
and we decided to investigate this possibility in the tetrahydropterin series.
The basic concept of this approach is illustrated by the coupling of nicotinic acid to a biologically active
molecule, quaternization with alkylating agents at the pyridine moiety and followed by reduction of the
pyridinium salt to the corresponding 1,4-dihydropyridine compound. Such a compound will be
distributed on dispension in the body including the brain. The dihydropyridine moiety will be oxidized to

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HETEROCYCLES, Vol. 77, No. 2, 2009
form the quaternary salt which due to its ionic character should be eliminated fast from the body while
the blood-brain-barrier should prevent its elimination from the brain. After cleavage of the nicotinoyl
residue the biologically active compound is regenerated in the brain in free form. A properly selected
carrier should either be eliminated or should be pharmacologically harmless. The overall result is a brain
specific sustained release of the active molecule.
O
H
H
N
R
BRAIN
BODY
delivery
O
H
O
H
H
H
N
R
N
R
in nvivo
in vivo oxidation
oxidation
O
O
N
R
N
R
enzymatic cleavage
enzymatic cleavage
O
O
O
+
O
+
N
N
R
R
blood-brain-barrier
excretion
RESULTS AND DISCUSSION
We applied the Bodor concept first to three synthetic analogs of BH4, the 6-methyl-, the 6,7-dimethyl-,
the 6-hydroxymethyl- and the 6,7-diphenyl-5,6,7,8-tetrahydropterin,11-13 respectively, all of which
showing some cofactor activity in vitro.

HETEROCYCLES, Vol. 77, No. 2, 2009
955
N
O
O
N
O
H
O
N
N
N
H
N
R
H
R
N
N
H
R
N
H
H
R1
N
O
O
H
H
R1
O
R1
N
H
N
H
N
N
H
N
H
N
H
R1
R
R1
R
R1
R
1
H
Me
Me
H
H
Me
6
H
Me
Me
H
H
Me
11
12 Me
13 Me
14 CH2Oibu H
15 C6H5 C6H5
H
H
H
Me
2
3
4
5
7
8
9
CH2Oibu H
C6H5 C6H5
CH2Oibu H
10 C6H5
C6H5
N
O
N
N
O
R2
O
N
O
N
H
R
N
H
R
N
X
N
H
H
R1
O
H
H
R1
X
N
H
N
H
H2N
N
H
R
R1
R1
H
Me Me
H
H
Me
H
R1
R2
R2
Et
R
R
X
16 Me
17 Me
18 CH2OH H
H
Me
19 Me
20 Me
21 CH2Oibu
22 Me
23 Me
Me
I
I
I
Br
Br
Br
26 Me
27 Me
28 Me
29 Me
30 Me
Me
Me
Me
Me
H
I
I
I
I
I
I
n-Pr
Me
Bn
Bn
Bn
n-C5H11
n-C8H17
n-C8H17
n-C8H17
24 CH2Oibu
25 C6H5
31 CH2Oibu
H
C6H5 Bn
Br
H
H
H
H
N
N
N
O
O
O
R2
R2
R2
O
N
O
O
N
N
N
H
H
H
R
R
R
N
N
N
H
H
R1
H
H
H
R1
X
O
H
H2N
R1
H2N
N
H
N
H
N
R
N
H
N
N
H
R1
R2
Bn
X
R
R1
R2
R1
R2
R
40 Me
41 Me
42 CH2OH
H
35 Me
36 Me
H
Me
Bn
Bn
Bn
32
33
34
Me H
Me Me n-C8H17
Me Me Bn
n-C8H17 I
Me Bn
Bn
I
Br
H
37 CH2Oibu
38 Me
39 Me
H
Me n-C5H11
Me n-C8H17
Scheme 1. Interonversions of pterins into 5-nicotinoyl-5,6,7,8-tetrahydropterin derivatives

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HETEROCYCLES, Vol. 77, No. 2, 2009
The starting N2-isobutyroylpterins (1-5) have first been reduced catalytically with Pt under H2-atmosphere
in a shaken apparatus to their corresponding 5,6,7,8-tetrahydro derivatives (6-10) which were then subject
to acylation with nicotinoyl chloride in pyridine at rt to form selectively the N5-nicotinoyl derivatives (11-
15). These substances were isolated as racemic mixtures due to the new chiral centers in 6- and 7 position,
respectively. 5,6,7,8-Tetrahydropterins possess in N5-position their most nucleophilic center in form of a
secundary amine type whereas the HN8 -side is part of a vinylogous amide moiety and is therefore less
reactive under the chosen reaction conditions. The high hydrolytic stability of the N5-acyl bond is seen
from the fact that treatment of 12-15 with sodium methoxide in MeOH at rt cleaves selectively only the
N2-isopropionyl group to give 16-18. Reactions of 12-15 with various alkylating agents such as methyl,
ethyl, n-propyl, n-pentyl and n-octyl iodide in MeOH or DMF as well as with benzyl bromide in DMSO
solution led under mild conditions at rt for 1- 5 days in high yields to the N-alkylated pyridinium salts
(19-31). Quarternization of the pyridine moiety takes place also selectively with 17 and 18 to yield 32-34.
Reduction of several pyridinium salts under mild basic conditions with sodium dithionite to the
corresponding 1,4-dihydronicotinoyl derivatives (35-39) worked only in a few cases (22-24, 28 and 29),
especially in the N-benzyl series. Selective removal of the isobutyroyl group by ammonia treatment at rt
resulted in the carrier molecules 40-42. The characterization of the newly synthesized pterin derivatives
1
was achieved by elemental analyses, H-NMR spectra (experimental part) and the determination of the
pKa values by the spectrophotometric method14 combined with UV-spectra (Tables 1, 2 and 3). On the
basis of the pKa-values the defined UV-spectra of the monocation, neutral form and monoanion as well
as the dication, monocation and zwitter iononic form have been determined to compare the equivalent
molecular species as further proof of the structural assignments.
Table 1. UV-Spectra of N5-Nicotinoyl- and N5-(1-alkylnicotinoyl)-5,6,7,8-tetrahydropterins
*
max
-5-nicotinoyl-5,6,7,8-
tetrahydropterin
pKa in
H2O
log e
!
molecular
species
pH
4.45 (4.03) 3.81
4.50 3.92 3.92
4.51 (4.18) (3.95) 3.82
N2-isobutyroyl- (11)
233 (260) 314
235 270 310
214 (244) (268) 304
+
o
-
3.16
9.44
1
7
12
+
o
-
4.33 4.47 (4.06) 3.84
4.33 4.50 3.92 3.92
4.51 (4.21) (3.97) 3.84
N2-isobutyroyl-
6-methyl-(12)
204 234 (262) 316
202 235 268 309
214 (242) (268) 306
3.19
9.68
1
7
12
+
o
-
4.31 4.46 (4.05) 3.82
4.51 (3.93) 3.93
4.52 (4.50) (3.96) 3.83
N2-isobutyroyl-
6,7-dimethyl-(13)
2046 235 (264) 317
237 (268) 310
207 (2414 (268) 300
3.16
9.59
1
7
12
+
o
-
4.34 4.45 (4.01) 3.76
4.51 3.91 3.93
4.51 (4.20 (3.98) 3.84
N2-isobutyroyl-
6-isobutyroyloxy-
methyl-(14)
206 233 (264) 316
235 266 310
213(246) (266) 300
3.00
9.47
1
7
12
+
o
-
4.54 (4.16) 3.83
4.63 4.55 (4.10) 3.91
4.66 (4.06) (3.89) 3.78
N2-isobutyroyl-
6,7-diphenyl-(15)
230 (262) 320
203 227 (268) 314
212(268) (288) 318
3.06
9.34
1
7
12

HETEROCYCLES, Vol. 77, No. 2, 2009
957
+
o
-
4.31
4.37
4.44
4.06 (3.68)
(3.99) 4.00
3.97 (3.60)
6-methyl- (16)
217
222
207
270 (316)
(276) 286
267 (310)
3.48
10.46
2.3
7
12
+
o
-
(4.29) 4.32 4.02 (3.65)
6,7-dimethyl-(17)
6-hydroxymethyl-(18)
(206) 218 270 (320)
3.55
10.33
2.3
7
12
4.35
4.40
(3.96) 3.98
3.94 (3.53)
222
209
(276) 287
267 (328)
+
o
-
4.36
4.41
4.10 (3.71)
(4.03) 4.05
216
223
270 (320)
(278) 287
3.38
10.30
2
6
12
4.57 (4.27) 4.00 (3.69)
206 (224) 268 (308)
-5,6,7,8-tetrahydro-
pterin
+ +
+
+ -
4.41
4.56
4.52
4.13 (3.76)
4.03 3.55
4.05 3.40
217
220
215
275 (312)
273 334
266 360
6-methyl-5-(1-n-octyl-
nicotinoyl)-
1.09
9.62
- 1
5
12
iodide (32)
+ +
+
+ -
4.44
4.57
4.52
4.14 (3.76)
4.05 3.57
4.07 3.43
218
222
215
276 (316)
273 334
266 363
6,7-dimethyl-5-(1-n-octyl-
nicotinoyl)-
1.12
9.46
- 1
5
12
iodide (33)
+ +
+
+ -
4.10 3.59
4.47 (4.41) 4.03 3.47
4.64 (4.05) 4.07 3.35
278 334
209 (220) 274 346
206 (254) 266 372
6,7-dimethyl-5-(1-benzyl-
nicotinoyl)- bromide (34)
1.07
9.81
- 1
5
12
*( ) shoulder
Table 2. UV-Spectra of N2-Isobutyroyl-5,6,7,8-tetrahydropterin-5-carbonyl-1-alkylpyridinium Salts
*
max
N2-Isobutyroyl-5,6,7,8-tetra-
hydropterin-5-carbonyl-
pKa in
H2O
log e
!
molecular
species
pH
4.58 4.09 (3.90)
4.60 4.02 3.80
4.64 (4.05) 3.63
214 274 (316)
227 264 320
219 (264) 324
6-methyl-(1-methyl-
pyridinium) iodide (19)
- 1.35
8.77
++
+
+ -
- 3
5
11
4.58 4.09 (3.95)
4.59 (4.02) 3.81
4.64 (4.06) 3.68
214 273 (308)
226 (268) 319
219 (266) 318
6,7-dimethyl-(1-methyl-
pyridinium) iodide (20)
- 1.23
8.97
++
+
+ -
- 3
5
11
4.57 4.07 (3.94)
4.58 3.99 3.78
4.64 (4.05) 3.62
214 274 (304)
226 266 320
219 (263) 338
6-isobutyroyloxymethyl
(1-methylpyridinium) iodide
(21)
- 1.18
8.83
++
+
+ -
- 3
5
11
4.49 4.03 3.78
4.39 (3.95) 3.59
4.57 (4.03) 3.43
212 276 324
230 (268) 335
205 (262) 351
6-methyl-(1-benzylyl-
pyridinium) bromide (22)
- 1.23
8.97
++
+
+ -
-4
5
11
(4.59) 4.09 (3.90)
4.47 (3.97) 3.62
(4.45) (4.07) 3.48
(209) 276 (320)
231 (272) 334
(226) (264) 351
6,7-dimethyl-(1-benzyl-
pyridinium) bromide (23)
- 1.66
9.09
++
+
+ -
- 4
5
11
(4.56) 4.06 (3.89)
4.44 (3.96) 3.61
4.63 (4.11) 3.48
( 212) 276 (316)
230 (268) 335
220 (264) 347
6-isobutyroyloxymethyl-
(1-benzyl-pyridinium) bromide
(24)
- 2.28
9.14
++
+
+ -
- 4
5
11
4.09 3.88
4.53 (4.05) 3.61
(4.50) (4.11) 3.47
279 320
232 (268) 336
(228) (264) 360
6,7-diphenyl-(1-benzyl-
pyridinium) bromide (25)
- 2.46
9.09
++
+
+ -
- 4.3
5
11
4.60 4.10 (3.90)
4.60 (4.02) 3.79
4.65 (4.07) 3.57
213 274 (316)
226 (266) 318
219 (264) 340
6,7-dimethyl-(1-ethyl-
pyridinium) iodide (26)
- 1.23
8.97
++
+
+ -
- 4
5
11

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HETEROCYCLES, Vol. 77, No. 2, 2009
4.61 4.09 (3.93)
4.60 (4.01) 3.75
4.64 (4.05) 3.53
213 274 (314)
226 (268) 319
220 (266) 338
6,7-dimethyl-(1-propyl-
pyridinium) iodide (27)
- 1.47
8.66
++
+
+ -
- 4
5
11
4.62 4.09 (3.93)
4.62 (4.00) 3.73
4.65 (4.06) 3.54
213 274 (316)
226 (268) 314
220 (264) 343
6,7-dimethyl-(1-n-pentyl-
pyridinium) iodide (28)
- 1.61
8.68
++
+
+ -
- 4
5
11
4.62 4.09 (3.92)
4.62 (3.97) 3.72
4.66 (4.07) 3.52
213 274 (316)
226 (268) 314
220 (264) 346
6,7-dimethyl-(1-n-octyl-
pyridinium) iodide (29)
- 1.71
9.09
++
+
+ -
- 4
5
11
4.63 4.09 (3.94)
4.62 (4.00) 3.73
4.64 (4.05) 3.52
213 274 (308)
226 (268) 320
220 (262) 343
6-methyl-(1-n-octyl-
pyridinium) iodide (30)
- 2.06
8.92
++
+
+ -
- 4
5
11
4.61 4.06 (3.94)
4.61 (3.96) 3.71
4.63 (4.02) 3.50
214 274 (304)
226 (266) 316
220 (264) 347
6-isobutyroyloxymethyl-
(1-n-octylpyridinium iodide
(31)
- 1.90
8.95
++
+
+ -
- 3
3
11
* ( ) shoulder
Table 3. UV-Spectra of N2-Isobutyroyl-5-(1-alkyl-1,4-dihydropyridine-3-carbonyl)-5,6,7,8-tetrahydropterin
*
max
N2-Isobutyroyl- -5,6,7,8-
tetrahydropterin
log e
!
molecular
species
pH
o
o
o
-6,7-dimethyl-5-(1-benzyl-1,4-
dihydropyridine-3-carbonyl)-
(35)
MeOH
4.46 4.46 3.94 3.89 3.81
204 234 278 316 356
203 233 282 ( 312) 356
204 232 276 313 353
-6-methyl-5-(1-benzyl-1,4-
dihydropyridine-3-carbonyl)-
(36)
MeOH
MeOH
4.43 4.46 3.98 (3.88) 3.81
4.46 4.44 3.98 3.92 3.84
-6-isobutyroyloxymethyl-
5-(1-benzyl-1,4-dihydro-
pyridine-3-carbonyl)- (37)
o
o
-6,7-dimethyl-5-(1-n-pentyl-
1,4-dihydropyridine-3-carbonyl)-
(38)
MeOH
MeOH
4.33 4.47 3.93 3.90 3.86
4.33 4.46 3.92 3.89 3.83
207 235 278 320 359
205 234 276 320 354
-6,7-dimethyl-5-(1-n-octyl-
1,4-dihydropyridine-3-carbonyl)-
(39)
-5,6,7,8-tetrahydropterin
o
-6,7-dimethyl-5-(1-benzyl-1,4-
dihydropyridine-3-carbonyl)-
(40)
MeOH
4.45 ( 4.44) 4.02
3.76
209 (217) 289
359
o
o
-6,7-dimethyl-5-(1-benzyl-1,4-
dihydropyridine-3-carbonyl)-
(41)
MeOH
MeOH
4.44 ( 4.40) 4.04
4.46 ( 4.43) 4.07
3.73
3.82
207 (218) 282
211 (220) 288
358
360
-6,7-dimethyl-5-(1-benzyl-1,4-
dihydropyridine-3-carbonyl)-
(42)
* ( ) shoulder

HETEROCYCLES, Vol. 77, No. 2, 2009
959
EXPERIMENTAL
General. TLC: precoated cellulose thin-layer sheets F 1440b LS 254 and silica gel thin-layer sheets F
1500 LS 254 from Schleicher and Schüll. Column chromatography: silica gel 60 from Merck. M.p.: Büchi
Melting Point B-545; no corrections. The pKa measurements were performed by the spectrophotometric
method.14 UV: Lambda 15 recording spectrometer from Perkin-Elmer: λmax (nm); log ε; (sh) shoulder.
1H-NMR: Bruker WM-250 spectrometer in δ (ppm) relative to TMS. Mass spectra: Firma Finnigan,
model MAT 312. Elemental analyses were performed in the microanalytical laboratory of Konstanz
University.
N2-Isobutyroylpterin (1): A suspenion of pterin (1.0 g, 6.1 mmol) in abs. pyridine (40 mL) was treated
with isobutyric anhydride (10 mL) under reflux for 4 h. It was evaporated and the residue recrystallized
from MeOH (180 mL) with charcoal to give 1.06 g (75%) colorless crystals, mp >290 °C (decomp.). pKa:
7.39. UV (pH 5): 214 (sh 4.13), 230 (4.16), 276 (4.14), 326 (3.87), 334 (sh 3.85); (pH 10): 224 (3.95),
1
252 (4.42), 282 (3.63), 339 (3.83). H-NMR (DMSO-d6): 1.15 (d, 6H, Me2C), 2.72 (sept, 1H, H-CMe2),
8.71 (d, 1H, H-C(6)), 8.92 (d, 1H, H-C(7)), 11.90 (s, 1H, H-N(3)), 12.32 (s, 1H, H-N). Anal. Calcd for
C10H11N5O2 (233.2): C, 51.50; H, 4.75; N, 30.03. Found: C, 51.60; H, 4.82; N, 30.01.
N2-Isobutyroyl-6-methylpterin (2): To a suspension of 6-methylpterin15,16 (2.0 g, 0.011 mmol) in abs.
pyridine (20 mL) was treated with isobutyric anhydride (5 mL) under reflux for 4.5 h. Charcoal was
added to the hot solution, filtered and after cooling evaporated to dryness. The residue was treated with
MeOH and the solid collected to give after drying in the oven at 100 °C 1.59 g (57%). Recrystallization
from MeOH/H2O gave 1.02 g (37%) colorless needles, mp 285 °C. pKa: 7.64. UV (pH 5): 228 (4.12), 278
1
(4.20), 335 (3.88); (pH 10): 224 (sh 3.97), 253 (4.42), 282 (sh 3.73), 344 (3.84). H-NMR, (DMSO-d6):
1.12 (d, 6H, C(Me2), 2.59 (s, 3H, H3C-C(6)), 2.76 (sept, 1H, H-CMe2), 8.79 (s, 1H, H-C(7)), 11.89 (s, H-
N(3)), 12.3 (bs, 1H, H-N). Anal. Calcd for C11H13N5O2 (247,3): C, 53.43; H, 5.30; N, 28.32. Found: C,
53.23; H, 5.31; N, 27.88.
N2-Isobutyroyl-6-isobutyroyloxymethylpterin (4): A suspension of 6-hydroxymethylpterin17 (4,0 g,
20.4 mmol) in abs. pyridine was treated with isobutyric anhydride (30 mL) under reflux for 5 h. After
cooling MeOH (20 mL) was added, stirred for 30 min, then evaporated, and coevaporated with toluene.
The residue was treated with EtOAc, the resulting precipitate collected, then dissolved in CHCl3 and
purified by silica-gel column chromatography with CHCl3/MeOH 30:1. The main fraction was separated,
evaporated and the residue recrystallized from n-hexane/CHCl3 to give 4.32 g (62 %) colorless crystals.
mp 183 °C. pKa: 7.24. UV (pH 5): 222 (sh 4.12), 233 (4.15), 281 (4.33), 335 (3.92); (pH 10): 224 (sh

960
HETEROCYCLES, Vol. 77, No. 2, 2009
1
3.98), 256 (4.47), 284 (sh 3.74), 346 (3.89). H-NMR (DMSO-d6): 1.10-1.20 (2d, 12H, 2 Me2C), 2.52
(sept, 1H, H-CMe2), 2.72 (sept, 1H, H-CMe2), 5.33 (s, 2H, CH2), 8.91 (s, 1H, H-C(7)), 11.80 (s, 1H, H-
N(3)), 12.22 (s, 1H, H-N). Anal. Calcd for C15H19N5O4 (333.4): C, 54.05; H, 5.75; N, 21.01. Found: C,
53.67; H, 5.75; N, 20.90.
N2-Isobutyroyl-6.7-diphenylpterin (5): A suspension of 6.7-diphenylpterin18 (5.3 g, 16.8 mmol) in abs.
pyridine (60 mL) was treated with isobutyric anhydride (15 mL) under reflux for 2.5 h. After cooling
down to 80 °C EtOH was added to the clear yellowish solution. On cooling a colorless precipitate
separated, was collected, washed with MeOH and dried at 100 °C to give 6.0 g (92%), mp 269 °C. pKa:
7.63. UV (pH 5): 225 (4.44), 256 (4.26), 296 (4.30), 365 (4.19); (pH 10): 221 (sh 4.37), 252 (sh 4.37),
258 (4.38), 371 (4.15). 1H-NMR, (DMSO-d6): 1.13 (d, 6H, C(Me2), 2.80 (m, 1H, H-CMe2), 7.26-7.53 (m,
10H, 2 ph), 9.82 (s, H-N(3)), 12.5 (bs, 1H, H-N). Anal. Calcd for C22H19N5O2 (385.4): C, 68.56; H, 4.97;
N, 18.17. Found: C, 67.94; H, 5.05; N, 17.97.
N2-Isobutyroyl-5-nicotinoyl-5,6,7,8-tetrahydropterin (11): In a shaking apparatus a suspension of N2-
isobutyroylpterin (1)(1.0 g, 4.3 mmol) in MeOH (100 mL) was reduced under H2-atmosphere in presence
of PtO2 (100 mg) as catalyst. After 24 h 2 equivalents of H2 were consumed. The suspension was
evaporated in vacuum to dryness and the residue treated with abs. pyridine (30 mL) and nicotinoyl
chloride hydrochloride (1.03 g, 5.8 mmol) with stirring overnight. EtOH (20 mL) was added, stirred for
1 h and then the precipitate filtered off. Recrystallization from EtOH/H2O (1:1) with charcoal gave
1
0.385 g (26%) of a yellowish crystal powder, mp 297-299 °C (decomp.). pK: 3.16, 9.44. H-NMR,
(DMSO-d6): 1.01 (d, 6H, C(Me2), 2.69 (sept, 1H, H-CMe2), 3.31 (m, 2H, H-C(7)), 3.48 (m, 2H, H-C(6)),
7.47 (s, 1H, H-N(8)), 7.38 (dd, 1H, nic-5), 7.79 (d, 1H, nic-4), 8.49 (d, 1H, nic-6), 8.59 (s, 1H, nic-2),
11.06 (s, H-N(3)), 11.38 (bs, 1H, H-N). Anal. Calcd for C16H18N6O3 x 0.25 H2O (346.9): C, 55.40; H,
5.38; N, 24.23. Found: C, 55.37; H, 5.54; N, 23.83.
N2-Isobutyroyl-6-methyl-5-nicotinoyl-5,6,7,8-tetrahydropterin (12): Analogous to the preceding
procedure with 2 (1.0 g, 4.05 mmol). The crude naterial was purified by recrystallization from MeOH (20
1
mL) with little charcoal to give 0.65 g (45%) colorless needles, mp 310 °C. pKa: 3.19, 9.68. H-NMR,
(DMSO-d6): 1.03 (d, 6H, C(Me2), 1.08 (d, 3H, Me-C(6)), 2.69 (sept, 1H, H-CMe2), 3.29-3.49 (m, 2H, H-
C(7)), 4.81 (m, 1H, H-C(6)), 7.43 (s, 1H, H-N(8)), 7.31 (dd, 1H, nic-5), 7.79 (d, 1H, nic-4), 8.49 (d, 1H,
nic-6), 8.58 (s, 1H, nic-2), 11.06 (s, H-N(3)), 11.32 (bs, 1H, H-N). Anal. Calcd for C17H20N6O3 (356.4): C,
57.29; H, 5.66; N, 23.58. Found: C, 57.10; H, 5.77; N, 23.45.

HETEROCYCLES, Vol. 77, No. 2, 2009
961
N2-Isobutyroyl-6,7-dimethyl-5-nicotinoyl-5,6,7,8-tetrahydropterin (13): A solution of N2-isobutyroyl-
6,7-dimethyl-5,6,7,8-tetrahydropterin (8)5 (10.78 g, 33.7 mmol) in abs. pyridine (200 mL) was cooled to
0°C and under N2-atmosphere nicotinoyl chloride hydrochloride (8,5 g, 47 mmol) added with stirring.
After stirring for 2 days under rt MeOH (10 ml) was added and the reaction mixture kept overnight in the
icebox. The precipitate was collected, washed with acetone and ether and dried in the vacuum desiccator
to give 7.3 g (58%) colorless powder, mp > 300 °C, From the filtrate were isolated another 1.46 g (12%).
1
pKa: 3.16, 9.59. H-NMR, (DMSO-d6): 0.85 (d, 3H, Me-C(7)), 1.03 (d, 6H, C(Me2), 1.17 (d, 3H, Me-
C(6)), 2.72 (sept, 1H, H-CMe2), 3.80 (m, 1H, H-C(7)), 4.59 (m, 1H, H-C(6)), 7.33 (bs, 1H, H-N(8)), 7.34
(dd, 1H, nic-5), 7.79 (d, 1H, nic-4), 8.48 (d, 1H, nic-6), 8.57 (s, 1H, nic-2), 11.08 (s, H-N(3)), 11.18 (bs,
1H, H-N). Anal. Calcd for C18H22N6O3 (370.4): C, 57.29; H, 5.66; N, 23.58. Found: C, 57.10; H, 5.77; N,
23.45.
N2-Isobutyroyl-6-isobutyroyloxymethyl-5-nicotinoyl-5,6,7,8-tetrahydropterin (14): Analogous to
procedure 11 with 4 (2.0, g, 6 mmol) in MeOH (180 mL) and PtO2 (0.36 g). The catalyst was filtered off
and the filtrate evaporated to dryness. The residue was dissolved in abs. pyridine (80 mL) and nicotinoyl
chloride hydrochloride (1.75 g, 7.75 mmol) added with stirring overnight. EtOH (10 mL) was added,
stirred for 30 min, evaporated and twice coevaporated with toluene/EtOH. The residue was recrystallized
from EtOH (30 mL) to give 1.18 g (44%) of colorless crystals, mp 300 °C (decomp.). pKa: 3.00, 9.47. 1H-
NMR, (DMSO-d6): 0.99 (d, 6H, CMe2)), 1.04 (d, 6H, C(Me2), 2.49 (sept, 1H, H-CMe2), 2.71 (sept, 1H,
H-CMe2), 3.35-3.51 (m, 2H, H-C(7)), 3.97 (m, 2H, O-CH2), 4.98 (bs, 1H, H-C(6)), 7.47 (bs, 1H, H-N(8)),
7.37 (dd, 1H, nic-5), 7.81 (d, 1H, nic-4), 8.51 (d, 1H, nic-6), 8.61 (s, 1H, nic-2), 11.02 (s, H-N(3)), 11.32
(bs, 1H, H-N). Anal. Calcd for C21H26N6O5 (442.5): C, 57.00; H, 5.42; N, 18.99. Found: C, 56.58; H, 5.89;
N, 18.94.
N2-Isobutyroyl-6,7-diphenyl-5-nicotinoyl-5,6,7,8-tetrahydropterin (15): Analogous to the preceding
procedure with 5 (5.48 g, 14.2 mmol) in MeOH (350 mL) and PtO2 (0.5 g). The resulting suspension was
evaporated, the residue dissolved in abs. pyridine (200 mL) and nicotinoyl chloride hydrochloride (3.4 g,
19.2 mmol) added. After stirring for 18 h the catalyst was filtered off and the filtrate evaporated to half of
its volume. EtOH (50 mL) was added, the precipitate collected and recrystallized from little EtOH/DMF
(1:1) to give 2.1 g (29%) of yellowish crystal powder, mp 289 °C. pKa: 3.06, 9.34. 1H-NMR, (DMSO-d6):
1.05 (d, 6H, C(Me2), 2.76 (sept, 1H, H-CMe2), 5.40 (m, 2H, H-C(7)), 5.65 (bs, 1H, H-C(6)), 6.80-7.20 (m,
10H, ph), 7.35 (dd, 1H, nic-5), 7.91 (d, 1H, nic-4), 8.17 (bs, 1H, H-N(8)), 8.53 (d, 1H, nic-6), 8.70 (s, 1H,
nic-2), 11.02 (s, H-N(3)), 11.32 (bs, 1H, H-N). Anal. Calcd for C28H26N6O3 x 0.5 H2O (503.6): C, 66.78; H,
5.40; N, 16.68. Found: C, 66.64; H, 5.47; N, 16.56.

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HETEROCYCLES, Vol. 77, No. 2, 2009
6-Methyl-5-nicotinoyl-5,6,7,8-tetrahydropterin (16): In abs. MeOH (180 mL) was dissolved Na (0.234
g, 10 mmol) and then under stirring 12 (3.0 g, 8.4 mmol) added. After stirring for 12 h the yellowish
solution was evaporated, the residue dissolved in H2O (80 mL), filtered, extracted with ether (30 mL) and
then neutralized with AcOH to pH 7. After cooling overnight the precipitate was collected and dried in a
1
vacuum desiccator to give 1.8 g (70%) colorless needles, mp 265-270 °C. pKa: 3.48, 10.46. H-NMR,
(DMSO-d6): 0.98 (d, 3H, Me-C(6)), 3.22 (m, 1H, H-C(7)), 3.45 (m, 1H, H-C(7)), 4.80 (m, 1H, H-C(6)),
6.08 (bs, 2H, NH2), 7.02 (s, 1H, H-N(8)), 7.30 (dd, 1H, nic-5), 7.81 (d, 1H, nic-4), 8.40 (d, 1H, nic-6),
8.54 (s, 1H, nic-2), 9.71 (s, H-N(3)). Anal. Calcd for C13H14N6O2 x H2O (304.3): C, 51.31; H, 5.30; N,
27.62. Found: C, 51.75; H, 4.90; N, 27.74.
6,7-Dimethyl-5-nicotinoyl-5,6,7,8-tetrahydropterin (17):
A
solution of 6,7-dimethyl-5,6,7,8-
tetrahydropterin dihydrochloride5 (11.3 g, 42 mmol) in abs. pyridine (600 mL) was cooled to 5 °C and
then under stirring and N2-atmosphere nicotinoyl chloride hydrochloride (9.5 g, 53.4 mmol) added. It was
stirred at rt over night, evaporated and coevaporated with toluene/EtOH. The residue was treated with
EtOH (100 mL), after cooling the precipitate collected and dried to give 10.4 g (74%) of the monohydro-
chloride salt. It was dissolved in H2O (300 mL), NaHCO3 (2.4 g) added, stirred for 1 h and then the
precipitate collected to give 9.0 g (61%) of a yellowish crystal powder, mp 295 °C (decomp.). pKa: 3.55,
1
10.30. H-NMR, (DMSO-d6): 0.98 (d, 3H, Me-C(6)), 1.05 (d, 3H, Me-C(7)), 3.65 (m, 1H, H-C(7)), 4.51
(m, 1H, H-C(6)), 6.08 (bs, 2H, NH2), 7.05 (s, 1H, H-N(8)), 7.30 (dd, 1H, nic-5), 7.75 (d, 1H, nic-4), 8.40
(d, 1H, nic-6), 8.60(s, 1H, nic-2), 9.70 (bs, H-N(3)). Anal. Calcd for C14H16N6O2 (300.3): C, 55.99; H,
5.37; N, 27.98. Found: C, 55.52; H, 5.47; N, 27.53.
6-Hydroxymethyl-5-nicotinoyl-5,6,7,8-tetrahydropterin (18): Analogous to procedure 16 with 14 (2.0
g, 4.5 mmol) in MeOH (100 mL) and Na (0.125 g). The resulting solid was recrystallized from
1
EtOH/H2O to give 0.55 g (40%) of a yellowish crystal powder, mp 220-224 °C. pKa: 3.38, 10.30. H-
NMR, (DMSO-d6): 3.12 (m, 2H, CH2), 3.35 (m, 1H, H-C(7)), 3.55 (m, 1H, H-C(7)), 4.59 (m, 1H, H-
C(6)), 4.95 (t, 1H, OH), 6.08 (bs, 2H, NH2), 7.04 (s, 1H, H-N(8)), 7.28 (dd, 1H, nic-5), 7.75 (d, 1H, nic-4),
8.44 (d, 1H, nic-6), 8.55 (s, 1H, nic-2), 9.70 (bs, H-N(3)).; EtOH: 1.04 (t, 3H, CH3), 3.40 (m, 2H, CH2),
4.36 (1H, OH), Anal. Calcd for C13H14N6O3. EtOH(348.4): C, 51.72; H, 5.79; N, 24.12. Found: C, 51.67;
H, 5.79; N, 24.01.
N2-Isobutyroyl-6-methyl-5-(1-methylnicotinoylium)-5,6,7,8-tetrahydropterin iodide (19): A solution
of 12 (2.06 g, 5.77 mmol) in abs. MeOH (200 mL) was treated with CH3I (20 mL) under stirring at rt for
4 days. The yellow solution was evaporated and the residue recrystallized from MeOH/H2O to give 1.88 g

HETEROCYCLES, Vol. 77, No. 2, 2009
963
(55%). Further recrystallization from H2O (20 mL) yielded 1.3 g (45%) of yellowish crystals, mp 293 °C
(decomp.). pKa: 8.77. 1H-NMR, (DMSO-d6): 1.02 (d, 6H, C(Me2), 1.08 (d, 3H, Me-C(6)), 2.72 (sept, 1H,
H-CMe2), 3.32 (dd, 1H, H-C(7)), 3.62 (m. 1H, H-C(7)), 4.35 (s, 3H-Me-N), 4.85 (m, 1H, H-C(6)), 7.69
(s, 1H, H-N(8)), 7.99 (dd, 1H, nic-5), 8.57 (d, 1H, nic-4), 8.93 (d, 1H, nic-6), 9.36 (s, 1H, nic-2), 11.09 (s,
H-N(3)), 11.43 (bs, 1H, H-N). Anal. Calcd for C18H23N6O3I (498.4): C, 43.39; H, 4.65; N, 16.86. Found:
C, 43.09; H, 4.83; N, 16.66.
N2-Isobutyroyl-6,7-dimethyl-5-(1-methylnicotinoylium)-5,6,7,8-tetrahydropterin
iodide
(20):
Analogous to the preceding procedure with 13 (6.05 g, 16,3 mmol) in MeOH (700 mL) with CH3I (25
mL). After 5 days was concentrated to 100 mL, cooled and the precipitate collected to give after drying in
a vacuum desiccator 5.65 g (66%) pure material, mp >300 °C. Recrystallization from H2O gave yellowish
1
crystals. pK: 8.97. H-NMR, (DMSO-d6): 0.86 (d, 3H, Me-C(7)), 1.04 (d, 6H, C(Me2), 1.23 (d, 3H, Me-
C(6)), 2.72 (sept, 1H, H-CMe2), 3.89 (m, 2H, H-C(7)), 4.31 (s, 3H, Me-N), 4.59 (m, 1H, H-C(6)), 7.18 (s,
1H, H-N(8)), 7.97 (dd, 1H, nic-5), 8.57 (d, 1H, nic-4), 8.86 (d, 1H, nic-6), 9.21 (s, 1H, nic-2), 11.15 (s, H-
N(3)), 11.23 (bs, 1H, H-N). Anal. Calcd for C19H25N6O3I. 0.5 H2O (521.4): C, 43.77; H, 5.03; N, 16.12.
Found: C, 43.65; H, 4.93; N, 16.33.
N2-Isobutyroyl-6-isobutyroyloxymethyl-5-(1-methylnicotinoylium)-5,6,7,8-tetrahydropterin iodide
(21): Analogous to the preceding procedure with 14 (0.975 g, 2.2 mmol) in abs. MeOH (80 mL) with
CH3I (10 mL) for 2 days. After evaporation the oily residue was treated with little EtOAc to form a solid
which was recrystallized from MeOH/EtOAc (1:4, 50 mL) to give 0.665 g (50 %) yellow needles and
1
from the mother liquid 0.51 g (39%), mp 200 °C. pKa: 8.83. H-NMR, (DMSO-d6): 1.02 (d, 6H, C(Me2),
1.08 (d, 6H, C(Me2), 2.69 (sept, 1H, H-CMe2), 2.49 (sept, 1H, H-CMe2), 3.53 (dd, 1H, H-C(7)), 3.67 (dd,
1H, H-C(7)), 3.89 (dd, 1H, OCH2), 4.01 (dd, 1H, OCH2), 4.35 (s, 3H-Me-N), 4.96 (m, 1H, H-C(6)), 7.66
(s, 1H, H-N(8)), 7.96 (dd, 1H, nic-5), 8.57 (d, 1H, nic-4), 8.88 (d, 1H, nic-6), 9.22 (s, 1H, nic-2), 11.12 (s,
.
H-N(3)), 11.39 (bs, 1H, H-N). Anal. Calcd for C22H29N6O5I 0.75 H2O (597.9): C, 44.19; H, 5.14; N,
14.05. Found: C, 44.26; H, 5.14; N, 14.05.
N2-Isobutyroyl-6-methyl-5-(1-benzylnicotinoylium)-5,6,7,8-tetrahydropterin bromide (22):
A
solution of 12 (0.52 g, 1.46 mmol) in DMSO (15 mL) was treated with benzyl bromide (0.35 g, 2.04
mmol) for 18 h at rt. Evaporation at high vacuum to an orange oil, which was dissolved in MeOH (20 ml)
and added dropwise with vigorous stirring into Et2O (80 mL). The precipitate was collected, washed with
Et2O and recrystallized from little iPrOH to give 0.41 g (52%) yellow crystals, mp 235 °C. pKa: 8.87. 1H-
NMR, (DMSO-d6): 0.98-1.12 (m, 9H, Me-C(6), C(Me2), 1.15 (d, 3H, Me-C(6)), 2.74 (sept, 1H, H-CMe2),

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HETEROCYCLES, Vol. 77, No. 2, 2009
3.35 (m, 1H, H-C(7)), 3.62 (dd. 1H, H-C(7)), 4.82 (m, 1H, H-C(6)), 5.80 (dd, 2H, N-CH2), 7.36 (m, 5H,
arom. H), 7.72 (s, 1H, H-N(8)), 8.08 (dd, 1H, nic-5), 8.69 (d, 1H, nic-4), 9.13 (d, 1H, nic-6), 9.47 (s, 1H,
nic-2), 11.09 (s, H-N(3)), 11.43 (bs, 1H, H-N). Anal. Calcd for C24H27N6O3Br . 0.5 H2O (536.4): C, 53.74;
H, 5.26; N, 15.67. Found: C, 53.66; H, 5.50; N, 15.27.
N2-Isobutyroyl-6,7-dimethyl-5-(1-benzylnicotinoylium)-5,6,7,8-tetrahydropterin bromide (23):
Analogous to the preceding procedure with 13 (5.0 g, 13.5 mmol) and benzyl bromide (2.3 mL, 19.5
mmol) in DMSO (125 mL) for 12 h at rt. The crude product was recrystallized from MeOH (150 mL) to
give 6.55 g (88%) yellowish crystals, mp 251 °C. pKa: 9.09. 1H-NMR, (DMSO-d6): 0.85 (d, 3H, Me-C(7)),
1.07 (d, 6H, Me2C), 1.22 (d, 3H, Me-C(6)), 2.78 (sept, 1H, H-CMe2), 3.93 (m, 1H, H-C(7)), 4.59 (m, 1H,
H-C(6)), 5.81 (dd, 2H, N-CH2), 7.35 (m, 5H, arom. H), 7.65 (s, 1H, H-N(8)), 8.09 (dd, 1H, nic-5), 8.70 (d,
1H, nic-4), 9.15 (d, 1H, nic-6), 9.51 (s, 1H, nic-2), 10.99 (s, H-N(3)), 11.28 (bs, 1H, H-N). Anal. Calcd
.
for C25H29N6O3Br 0.5 H2O (550.4): C, 54.55; H, 5.49; N, 15.27. Found: C, 54.66; H, 5.63; N,
15.37.
N2-Isobutyroyl-6-isobutyroyloxymethyl)-5-(1-benzylnicotinoylium)-5,6,7,8-tetrahydropterin
bromide (24): Analogous to the preceding prucedure with 14 (0.74 g, 1,67 mmol) and benzyl bromide
(0.4 mL, 2.34 mmol) in DMSO (20 mL) for 18 h at rt. The crude product was recrystallized from
EtOAc/MeOH to give 0.61 g (58 %) yellow crystals, mp 263 °C. pKa: 9.14. 1H-NMR, (DMSO-d6): 1.01-
1.11 (m, 12H, 2 Me2C), 2.49 (sept, 1H, H-CMe2), 2.75 (sept, 1H, H-CMe2), 3.47 (m, 1H, H-C(7)), 3.61
(m, 1H, H-C(7)), 3.85 (dd, 1H, H2C-C(6)), 4.00 (dd, 1H, H2C-C(6)), 5.92 (dd, 2H, N-CH2), 7.33 (m, 5H,
arom. H), 7.72 (s, 1H, H-N(8)), 8.10 (dd, 1H, nic-5), 8.67 (d, 1H, nic-4), 9.15 (d, 1H, nic-6), 9.45 (s, 1H,
nic-2), 10.95 (s, H-N(3)), 11.44 (bs, 1H, H-N). Anal. Calcd for C28H33N6O5Br . 0.5 H2O (622.5): C, 54.02;
H, 5.50; N, 13.50. Found: C, 54.07; H, 5.48; N, 13.51.
N2-Isobutyroyl-6,7-diphenyl-5-(1-benzylnicotinoylium)-5,6,7,8-tetrahydropterin
bromide
(25):
Analogous to the preceding procedure with 15 (1.0 g, 2.02 mmol) and benzyl bromide (0.46 g, 2.7 mmol)
in DMSO (20 mL) at 60 °C for 5 h. The crude product was recrystallized from MeOH/H2O (1:1, 150 mL)
1
to give 1.1 g (79%) yellow needles, mp 269 °C. pKa: 9.09. H-NMR, (DMSO-d6): 1.10 (m, 6H, Me2C),
2.82 (sept, 1H, H-CMe2), 5.51 (d, 1H, H-C(7)), 3.88 (d, 1H, H-C(6)), 5.88 (dd, 2H, N-CH2), 7.03-7.44 (m,
10H, arom. H), 8.12 (dd, 1H, nic-5), 8.47 (s, 1H, H-N(8)), 8.78 (d, 1H, nic-4), 9.18 (d, 1H, nic-6), 9.66 (s,
1H, nic-2), 11.16 (s, H-N(3)), 11.47 (bs, 1H, H-N). Anal. Calcd for C35H33N6O5Br . H2O (683.6): C, 61.49;
H, 5.16; N, 12.29. Found: C, 61.37; H, 5.61; N, 12.05.

HETEROCYCLES, Vol. 77, No. 2, 2009
965
N2-Isobutyroyl-6,7-dimethyl-5-(1-ethylnicotinoylium)-5,6,7,8-tetrahydropterin
iodide
(26):
Analogous to the preceding procedure with 13 (0.82 g, 2.2 mmol) and C2H5I (2 mL) in DMSO (10 mL) at
rt for 2 days. The crude product was recrystallized from EtOH to give 0.8 g (67%) yellow crystals, mp
1
290 °C. pKa: 8.97. H-NMR, (DMSO-d6): 0.85 (d, 3H, Me-C(7)), 1.02 (d, 6H, C(Me2), 1.21 (d, 3H, Me-
C(6)), 1.44 (t, 3H, H3C-CH2), 2.72 (sept, 1H, H-CMe2), 3.91 (m, 1H, H-C(7)), 4.62 (m, 3H, H2C-N, H-
C(6)), 7.62 (s, 1H, H-N(8)), 8.00 (dd, 1H, nic-5), 8.60 (d, 1H, nic-4), 8.99 (d, 1H, nic-6), 9.39 (s, 1H, nic-
.
2), 11.13 (s, H-N(3)), 11.23 (bs, 1H, H-N). Anal. Calcd for C20H27N6O3I 0.5 H2O (535.4): C, 44.87; H,
5.27; N, 15.70. Found: C, 44.72; H, 5.32; N, 15.46.
N2-Isobutyroyl-6,7-dimethyl-5-(1-n-propylnicotinoylium)-5,6,7,8-tetrahydropterin iodide (27):
Analogous to the preceding procedure with 13 (1.0 g, 2.7 mmol) and n-C3H7I (2 mL) in DMF (40 mL) at
100°C for 8 h. The reaction solution was evaporated, twice coevaporated with EtOH. The crude product
was recrystallized from EtOH (30 mL) to give 1.1 g (72%) orange crystals, mp 288-290 °C (decomp.).
pKa: 8.66. 1H-NMR, (DMSO-d6): 0.79 (t, 3H, H3C-CH2CH2), 0.91 (d, 3H, Me-C(7)), 1.01 (d, 6H, C(Me2),
1.21 (d, 3H, Me-C(6)), 1.44 (t, 3H, H3C-CH2), 1.81 (m, 2H, CH3CH2CH2), 2.72 (sept, 1H, H-CMe2), 3.91
(m, 1H, H-C(7)), 4.54 (m, 3H, H2C-N, H-C(6)), 7.64 (s, 1H, H-N(8)), 8.02 (dd, 1H, nic-5), 8.65 (d, 1H,
nic-4), 8.98 (d, 1H, nic-6), 9.37 (s, 1H, nic-2), 11.15 (s, H-N(3)), 11.30 (bs, 1H, H-N). Anal. Calcd for
C21H29N6O3I (540.4): C, 46.47; H, 5.41; N, 15.55. Found: C, 46.41; H, 5.46; N, 15.09.
N2-Isobutyroyl-6,7-dimethyl-5-(1-n-pentylnicotinoylium)-5,6,7,8-tetrahydropterin iodide (28):
Analogous to the preceding procedure with 13 (1.04 g, 2.8 mmol) and n-C5H11I (0.7 g, 3.53 mmol) in
DMF (40 mL) at 150 °C for 4 h. The reaction solution was evaporated, twice coevaporated with EtOH.
The crude product was dissolved in little EtOH and dropwise added to stirring cold n-hexane (200 mL).
The precipitate was collected and recrystallized from acetone to give 1.4 g (88 %) orange crystals, mp
1
255-257 °C. pKa: 8.68. H-NMR, (DMSO-d6): 0.78-1.01 (m, 10H, H3C-CH2CH2, Me-C(7)), 1.02 (d, 6H,
C(Me2), 1.21 (d, 3H, Me-C(6)), 1.78 (t, 2H, H3C-CH2CH2CH2), 2.73 (sept, 1H, H-CMe2), 3.91 (m, 1H, H-
C(7)), 4.56 (m, 3H, H2C-N, H-C(6)), 7.64 (s, 1H, H-N(8)), 8.04 (dd, 1H, nic-5), 8.64 (d, 1H, nic-4), 8.98
(d, 1H, nic-6), 9.33 (s, 1H, nic-2), 11.14 (s, H-N(3)), 11.27 (bs, 1H, H-N). Anal. Calcd for C23H33N6O3I
(568.5): C, 48.60; H, 5.85; N, 14.78. Found: C, 48.11; H, 5.86; N, 14.77.
N2-Isobutyroyl-6,7-dimethyl-5-(1-n-octylnicotinoylium)-5,6,7,8-tetrahydropterin iodide (29):
Analogous to the preceding procedure with 13 (1.0 g, 2.7 mmol) and n-C8H17I (1.0 g, 4.16 mmol) in DMF
(40 mL) at 150 °C for 3 h. The reaction solution was evaporated, twice coevaporated with EtOH. The
crude product was dissolved in little EtOH and dropwise added to stirring cold n-hexane (200 mL). The

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HETEROCYCLES, Vol. 77, No. 2, 2009
crude product was recrystallized from EtOAc/EtOH to give 1.15 g (70 %) orange crystals, mp 245-
1
247 °C. pKa: 8.77. H-NMR, (DMSO-d6): 0.81-1.23 (m, 25H, H3C-(CH2,)5 Me-C(6), Me2C, Me-C(7)),
1.78 (m. 2H, H2C-H2C-N), 2.78 (sept, 1H, H-CMe2), 4.56 (m, 4H, H2C-N, H-C(7), H-C(6)), 7.63 (s, 1H,
H-N(8)), 8.03 (dd, 1H, nic-5), 8.63 (d, 1H, nic-4), 8.98 (d, 1H, nic-6), 9.34 (s, 1H, nic-2), 11.14 (s, H-
N(3)), 11.26 (bs, 1H, H-N). Anal. Calcd for C26H39N6O3I (610.6): C, 51.15; H, 6.44; N, 13.77. Found: C,
50.88; H, 6.34; N, 13.50.
N2-Isobutyroyl-6-methyl-5-(1-n-octylnicotinoylium)-5,6,7,8-tetrahydropterin iodide (30):
Analogous to the preceding procedure with 12 (2.0 g, 5.6 mmol) and n-C8H17I (1.12 mL) in DMF (60 mL)
at 150 °C for 6 h. The reaction solution was evaporated, twice coevaporated with EtOH. The crude
product was heated with H2O (50 mL) and EtOH added till solution took place. Charcoal was added,
filtered and the filtrate put in the icebox to get 1.52 g (46 %) yellow crystals, mp 203-205 °C. pKa: 8.92.
1H-NMR, (DMSO-d6): 0.83 (t, 3H, H3C(CH2)7), 1.00-1.23 (m, 19H, H3C-(CH2,)5 Me-C(6), Me2C), 1.77 (m.
2H, H2C-H2C-N), 2.69 (sept, 1H, H-CMe2), 3.34 (m, 1H, H-C(7)), 3.62 (m. 1H, H-C(7)), 4.56 (t, 2H,
H2C-N), 4.83 (m, 1H, H-C(6)), 7.70 (s, 1H, H-N(8)), 8.03 (dd, 1H, nic-5), 8.62 (d, 1H, nic-4), 8.99 (d, 1H,
nic-6), 9.34 (s, 1H, nic-2), 11.10 (s, H-N(3)), 11.41 (bs, 1H, H-N). Anal. Calcd for C25H37N6O3I . 0.5 H2O
(605.6): C, 49.58; H, 6.32; N, 13.87. Found: C, 49.73; H, 6.31; N, 13.70.
N2-Isobutyroyl-6-isobutyroyloxymethyl-5-(1-n-octylnicotinoylium)-5,6,7,8-tetrahydropterin iodide
(31): Analogous to the preceding procedure with 14 (3.0 g, 6.78 mmol) and n-C8H17I (1.75 mL) in DMF
(90 mL) at 150 °C for 4 h. The reaction solution was evaporated, twice coevaporated with EtOH and the
residue dissolved in EtOAc (100 mL). Cooling overnight yielded 3.54 g (77%) crude material.
Recrystallization from EtOAc/EtOH (5:4, 90 mL) gave 2.67 g (58%) yellow crystals, mp 235-236 °C.
1
pKa: 8.95. H-NMR, (DMSO-d6): 0.83 (t, 3H, H3C(CH2)7), 1.00-1.23 (m, 16H, H3C-(CH2,)5, Me2C), 1.77
(m. 2H, H2C-H2C-N), 2.69 (sept, 1H, H-CMe2), 3.52 (m, 1H, H-C(7)), 3.65 (m. 1H, H-C(7)), 3.89 (dd, 1H,
H2C-C(6)); 3.99 (dd, 1H, H2C-C(6)); 4.52 (t, 2H, H2C-N), 4.97 (m, 1H, H-C(6)), 7.69 (s, 1H, H-N(8)),
8.04 (dd, 1H, nic-5), 8.61 (d, 1H, nic-4), 8.98 (d, 1H, nic-6), 9.32 (s, 1H, nic-2), 11.08 (s, H-N(3)), 11.41
(bs, 1H, H-N). Anal. Calcd for C29H34N6O3I (682.6): C, 51.03; H, 6.35; N, 12.31. Found: C, 50.96; H,
6.39; N, 12.08.
6-Methyl-5-(1-n-octylnicotinoylium)-5,6,7,8-tetrahydropterin iodide (32): A solution of 16 (0.5 g,
1.64 mmol) in DMF (10 mL) was treated with n-octyl iodide (0.38 mL) at 100 °C for 6 h. It was
evaporated, coevaporated with EtOH and the residue recrystallized from EtOH/MeOH to give 0.6 g
1
(67%) yellowish crystals, mp 206-208 °C. pKa: 1.09, 9.62. H-NMR, (DMSO-d6): 0.84 (t, 3H, H3C-
(CH2)7), 0.97 (d, 3H, Me-C(6)), 1.01-1.24 (m, 10H, H3C-(CH2)5), 1.79 (m, 2H, N-CH2CH2), 3.23 (m, 1H,

HETEROCYCLES, Vol. 77, No. 2, 2009
967
H-C(7)), 3.55 (m, 1H, H-C(7)), 4.57 (t, 2H, N-CH2), 4.77 (m, 1H, H-C(6)), 6.25 (bs, 2H, NH2), 7.33 (s,
1H, H-N(8)), 8.01 (dd, 1H, nic-5), 8.57 (d, 1H, nic-4), 8.97 (d, 1H, nic-6), 9.30 (s, 1H, nic-2), 9.80 (s, H-
N(3)). Anal. Calcd for C21H31N6O2I (526.4): C, 47.92; H, 5.96; N, 15.96. Found: C, 47.76; H, 5.99; N,
15.94.
6,7-Dimethyl-5-(1-n-octylnicotinoylium)-5,6,7,8-tetrahydropterin iodide (33): Analogous to the
preceding procedure with 17 (2.5 g, 8.3 mmol) in DMF (70 mL) and n-octyl iodide (1.85 mL) at 150 °C
for 3 h. Recrystallization from EtOH (25 mL) yielded 3.94 g (79%) yellowish plates, mp 180 °C. pKa:
1.07, 9.81. 1H-NMR, (DMSO-d6): 0.83 (t, 3H, H3C-(CH2)7), 0.98 (d, 3H, Me-C(6)), 1.15 (d, 3H, Me-C(7)),
1.24 (m, 10H, H3C-(CH2)5), 1.79 (m, 2H, N-CH2CH2), 3.81 (m, 1H, H-C(7)), 4.56 (t, 2H, N-CH2), 4.57 (m,
1H, H-C(6)), 6.17 (bs, 2H, NH2), 7.32 (s, 1H, H-N(8)), 8.01 (dd, 1H, nic-5), 8.58 (d, 1H, nic-4), 8.95 (d,
1H, nic-6), 9.31 (s, 1H, nic-2), 9.80 (s, H-N(3)). Anal. Calcd for C22H33N6O2I . 0.5 H2O (549.6): C, 48.09;
H, 6.24; N, 15.30. Found: C, 47.84; H, 6.43; N, 15.08.
6,7-Dimethyl-5-(1-benzylnicotinoylium)-5,6,7,8-tetrahydropterin bromide (34): Analogous to the
preceding procedure with 17 (0.253 g, 0.84 mmol) in DMSO (10 mL) and benzyl bromide (0.1 g, 1.18
mmoL) at rt for 18 h. After evaporation in high vacuum the residue was recrystallized from EtOH (15
1
mL) to give 0.294 g (74%) of yellowish crystals, mp 275 °C (decomp.). pKa: 1.07, 9.81. H-NMR,
(DMSO-d6): 0.83 (d, 3H, Me-C(7)), 1.15 (d, 3H, Me-C(6)), 3.85 (m, 1H, H-C(7)), 4.50 (m, 1H, H-C(6)),
5.84 (s, 2H, N-CH2), 6.31 (bs, 2H, NH2), 7.35 (m, 6H, arom. H, H-N(8)), 8.03 (dd, 1H, nic-5), 8.65 (d, 1H,
.
nic-4), 9.06 (d, 1H, nic-6), 9.51 (s, 1H, nic-2), 9.82 (s, H-N(3)). Anal. Calcd for C21H23N6O2Br 0.5 H2O
(480.4): C, 52.51; H, 5.04; N, 17.50. Found: C, 52.53; H, 5.24; N, 16.84.
N2-Isobutyroyl-6-methyl-5-(1-benzyl-1,4-dihydronicotinoyl)-5,6,7,8-tetrahydropterin
(35):
A
solution of 22 (0.2 g, 0.37 mmol) and NaHCO3 (0.125 g) under N2-atmosphere was treated with EtOAc (6
mL). Under vigorous stirring Na2S2O4 (0.26 g, 1.5 mmol) was added in small portions and after 1 h the
precipitate collected. The solid was washed with H2O, EtOAc and ether and dried in a vacuum desiccator
to give 0.145 g (87%) crude material. Recrystallization from little EtOH yielded 0.086 g (52%) of a
1
colorless powder, mp 210 °C. H-NMR, (DMSO-d6): 0.88 (m, 3H, Me-C(6)), 1.14 (d, 6H, Me2C), 2.74
(sept, 1H, H-CMe2), 2.93 (dd, 1H, nic-4'), 3.15 (dd, 1H, nic-4''), 3.19 (m, 2H, H-C(7)), 4.19 (s, 2H, N-
CH2), 4.51 (m, 2H, H-C(6), nic-5), 5.84 (dd, 1H, nic-6), 6.30 (s, 1H, nic-2), 6.98 (s, 1H, H-N(8)), 7.15 (m,
5H, arom. H), 11.22 (s, H-N(3)), 11.24 (bs, 1H, H-N). Anal. Calcd for C24H28N6O3 (448.5): C, 64.27; H,
6.29; N, 18.74. Found: C, 63.83; H, 6,23; N, 18.58.

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N2-Isobutyroyl-6,7-dimethyl-5-(1-benzyl-1,4-dihydronicotinoyl)-5,6,7,8-tetrahydropterin (36):
A
solution of 23 (3.9 g, 7.2 mmol) and NaHCO3 (2.4 g, 28.8 mmol) in H2O (225 mL) was kept under N2-
atmosphere. Under stirring Na2S2O4 (2.4 g, 28.8 mmol) was added in small portion within 15 min. and the
resulting precipitate collected after 3 h. The crude material was recrystallized from abs. EtOH (200 mL)
under nitrogen to give 1.41 g (42 %) of yellowish needles, mp 230 °C. 1H-NMR, (DMSO-d6): 0.75 (d, 3H,
Me-C(7)), 1.12 (d, 6H, Me2C), 1.15 (d, 3H, Me-C(6)), 2.77 (sept, 1H, H-CMe2), 2.93 (dd, 1H, nic-4'),
3.15 (dd, 1H, nic-4''), 3.45 (m, 1H, H-C(7)), 4.14 (m, 3H, N-CH2, H-C(6)), 4.49 (m, 1H, nic-5), 5.84 (dd,
1H, nic-6), 6.31 (s, 1H, nic-2), 6.83 (s, 1H, H-N(8)), 7.15 (m, 5H, arom. H), 11.18 (m, H-N(3), H-N).
.
Anal. Calcd for C25H30N6O3 0.5 H2O (471.6): C, 63.68; H, 6.63; N, 17.82. Found: C, 64.01; H, 6,48; N,
17.78.
N2-Isobutyroyl-6-isobutyroyloxymethyl-5-(1-benzyl-1,4-dihydronicotinoyl)-5,6,7,8-tetrahydropterin
(37): A solution of 24 (0.2 g, 0.32 mmol) and NaHCO3 (0.11 g, 1.3 mmol) in H2O (10 mL) was treated
under N2-atmosphere and stirring with Na2S2O4 (0.226 g, 1.3 mmol) for 1 h at rt. The reaction solution
was kept overnight in the icebox, the resulting precipitate was collected and recrystallized from little
MeOH to yield 0.1 g (42%) of colorless crystals, mp 208 °C. 1H-NMR, (DMSO-d6): 1.02 (d, 6H, Me2C),
1.12 (d, 6H, Me2C), 2.48 (sept, 1H, H-CMe2), 2.74 (sept, 1H, H-CMe2), 2.94 (dd, 1H, nic-4'), 3.17 (dd,
1H, nic-4''), 3.76 (m, 2H, H-C(7)), 3.85 (dd, 2H, H2C-C(6)), 4.20 dd, 2H, N-CH2), 4.1 (m, 1H, nic-5),
4.55 (m, 1H, H-C(6)), 5.83 (dd, 1H, nic-6), 6.30 (s, 1H, nic-2), 7.00 (d, 1H, H-N(8)), 7.16 (m, 5H, arom.
.
H), 11.26 (s, 1H, H-N(3)), 11.28 (s, 1H, H-N). Anal. Calcd for C28H34N6O5 0.5 H2O (543.6): C, 61.86; H,
6.49; N, 15.46. Found: C, 61.54; H, 6,22; N, 15.25.
N2-Isobutyroyl-6,7-dimethyl-5-(1-n-pentyl-1,4-dihydronicotinoyl)-5,6,7,8-tetrahydropterin (38):
Analogous to the preceding procedure with 28 (0.25 g, 0.44 mmol) and NaHCO3 (0.15 g, 1.76 mmol) in
H2O (10 mL) under N2-atmosophere. After successive addition of Na2S2O4 (0.306 g, 1.76 mmol) was
stirred for 1 h, then cooled in the icebox and the precipitate collected after 6 h to give 62 mg (32%) of
1
yellowish crystals, mp >200 °C (decomp.). H-NMR, (DMSO-d6): 0.84 (m. 6H, H3C(CH2)5, Me-C(7)),
1.11-1.19 (m, 15H, Me2C, Me-C(6), H3C(CH2)3), 2.74 (sept, 1H, H-CMe2), 2.90 (m, 3H, N-CH2, nic-4'),
3.11 (dd, 1H, nic-4''), 3.47 (m, 1H, H-C(7)), 4.20 (dd, 2H, H2C-C(6)), 4.45 (m, 1H, nic-5), 5.76 (dd, 1H,
nic-6), 6.20 (s, 1H, nic-2), 6.89 (d, 1H, H-N(8)), 11.20 (bs, 2H, H-N(3), H-N). Anal. Calcd for
.
C23H34N6O3 0.5 H2O (543.6): C, 61.86; H, 6.49; N, 15.46. Found: C, 61.54; H, 6,22; N, 15.25.
N2-Isobutyroyl-6,7-dimethyl-5-(1-n-octyl-1,4-dihydronicotinoyl)-5,6,7,8-tetrahydropterin (39):
Analogous to the preceding procedure with 29 (0.25 g, 0.41 mmol) and NaHCO3 (0.15 g, 1.76 mmol) in

HETEROCYCLES, Vol. 77, No. 2, 2009
969
H2O (10 mL) under N2-atmosphere. After successive addition of Na2S2O4 (0.285 g, 1.64 mmol) was
stirred for 1 h, then cooled in the icebox and the precipitate collected after 4 h to give 0.10 g (50%) of
1
yellowish crystals, mp > 200 °C (decomp.). H-NMR, (DMSO-d6): 0.79 (m. 6H, H3C(CH2)7, Me-C(7)),
1.02-1.26 (m, 21H, Me2C, Me-C(6), H3C(CH2)6), 2.74 (sept, 1H, H-CMe2), 2.90 (m, 3H, N-CH2, nic-4'),
3.07 (dd, 1H, nic-4''), 3.47 (m, 1H, H-C(7)), 4.18 (dd, 2H, H2C-C(6)), 4.45 (m, 1H, nic-5), 5.76 (dd, 1H,
nic-6), 6.22 (s, 1H, nic-2), 6.88 (d, 1H, H-N(8)), 11.20 (bs, 2H, H-N(3), H-N). Anal. Calcd for
.
C26H40N6O3 0.5 H2O (493.7): C, 63.26; H, 8.37; N, 17.02. Found: C, 62.94; H, 8.06; N, 17.12.
6-Methyl-5-(1-benzyl-1,4-dihydronicotinoyl)-5,6,7,8-tetrahydropterin (40): A suspension of 35 (0.751
g, 1.67 mmol) in MeOH (40 mL) was treated under N2-atmosphere with K2CO3 (0.255 g, 1.84 mmol) at rt
and stirring overnight. It was evaporated and the resulting oil recrystallized from H2O (15 mL) to give
1
after drying in a vacuum desiccator 0.393 g (60%) of yellowish crystal powder, mp 232 °C. H-NMR,
(DMSO-d6): 0.88 (d, 3H, Me-C(6)), 1.14 (d, 6H, Me2C), 2.88 (dd, 1H, nic-4'), 3.07 (dd, 1H, nic-4''), 3.09
(m, 2H, H-C(7)), 4.18 (s, 2H, N-CH2), 4.45 (m, 2H, H-C(6)), nic-5), 5.82 (d, 1H, nic-6), 6.28 (bs, 2H,
NH2), 6.32 (s, 1H, nic-2), 6.57 (s, 1H, H-N(8)), 7.25 (m, 5H, arom. H), 10.5 (bs, H-N(3)). Anal. Calcd for
.
C20H22N6O2 H2O (396.5): C, 60.59; H, 6.10; N, 21.20. Found: C, 60.34; H, 6,12; N, 20.93.
6,7-Dimethyl-5-(1-benzyl-1,4-dihydronicotinoyl)-5,6,7,8-tetrahydropterin (41): Analogous to the
preceding procedure with 36 (2.51 g, 4,55 mmol) in MeOH (110 mL) under N2-atmosphere with K2CO3
(0.6.85 g, 0.49 mmol) at rt and stirring overnight. The resulting precipitate gave after drying in a vacuum
1
desiccator 1.42 g (72%) analytically pure yellowish crystals, mp 255 °C. H-NMR, (DMSO-d6): 0.75 (d,
3H, Me-C(6)), 1.02 (d, 3H, Me-C(6)), 2.90 (dd, 1H, nic-4'), 3.10 (dd, 1H, nic-4''), 3.35 (1H, H-C(7)), 4.13
(m. 1H, H-C(6)), 4.16 (dd, 2H, N-CH2), 4.45 (m, 1H, nic-5), 5.84 (d, 1H, nic-6), 6.04 (bs, 2H, NH2), 6.31
(s, 1H, nic-2), 6.52 (s, 1H, H-N(8)), 7.25 (m, 5H, arom. H), 9.80 (bs, H-N(3)). Anal. Calcd for
C21H24N6O2 (392.5): C, 64.27; H, 6.16; N, 21.41. Found: C, 63.95; H, 6,123; N, 21.33.
6-Hydroxymethyl-5-(1-benzyl-1,4-dihydronicotinoyl)-5,6,7,8-tetrahydropterin (42): Analogous to the
preceding procedure with 37 (0.22 g, 0.41 mmol) and K2CO3 (66 mg) in MeOH (12 mL). It was
evaporated and the residue recrystallized from H2O (5 mL) to give 94 mg (53%) of yellowish crystals, mp
210 °C. 1H-NMR, (DMSO-d6): 2.89 (dd, 1H, nic-4'), 3.09 (m, 2H, H-C(7)), 3.12 (dd, 1H, nic-4''), 3.49 (m,
2H, H2C-C(6)), 4.17 (s, 2H, N-CH2), 4.25 (m, 2H, H-C(6)), 4.45 (dt, 1H, nic-5), 5.80 (d, 1H, nic-6), 6.04
(bs, 2H, NH2), 6.44 (s, 1H, nic-2), 6.61 (s, 1H, H-N(8)), 7.25 (m, 5H, arom. H), 10.1 (bs, H-N(3)). Anal.
.
Calcd for C20H22N6O3 2 H2O (430.5): C, 55.81; H, 6.09; N, 19.52. Found: C, 55.64; H, 5.86; N, 18.92.

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