Design, synthesis, and evaluation of potential GAR and AICAR transformylase inhibitors

Article abstract of DOI:10.1016/S0968-0896(98)00040-6

The synthesis and evaluation of 1 4 as potential inhibitors of GAR Tfase and AICAR Tfase are detailed. Copyright (C) 1998 Elsevier Science Ltd.

Full text of DOI:10.1016/S0968-0896(98)00040-6

BIOORGANIC &
MEDICINAL
CHEMISTRY
Bioorganic & Medicinal Chemistry 6 (1998) 643±659
Design, Synthesis, and Evaluation of Potential GAR and
AICAR Transformylase Inhibitors
Dale L. Boger,a,* Monica J. Kochanny,a Hui Cai,a Diane Wyatt,b Paul A. Kitos,b
M. S. Warren,c J. Ramcharan,c Lata T. Gooljarsinghc and Stephen J. Benkovicc
aDepartment of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA
bDepartment of Biochemistry, University of Kansas, Lawrence, Kansas 66045, USA
cDepartment of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, USA
Received 25 February 1997; accepted 4 August 1997
AbstractÐThe synthesis and evaluation of 1±4 as potential inhibitors of GAR Tfase and AICAR Tfase are detailed.
# 1998 Elsevier Science Ltd. All rights reserved.
Introduction
was to maintain the key elements of the folate±enzyme
interaction at the active site but dispense with the entire
benzoyl glutamate side chain, providing much smaller
potential inhibitors and avoiding the unpredictable
issues of active transport and polyglutamylation critical
to the intracellular accumulation of cofactor analogues
detailed to date. Moreover, in the absence of imine
formation, ine€ective competitive inhibition with the
endogenous folate cofactors was expected potentially to
convey selectivity for GAR and AICAR Tfase over
other folate dependent enzymes not directly engaged in
a formyl transfer reaction. The design of the GAR
Tfase inhibitors was carried out based on the X-ray
structures of phosphate bound GAR Tfase and GAR
Tfase bound with the inhibitor 1476U89.4 Model
building of potential bound inhibitors employed
MacroModel (AMBER and OPLSA force ®elds) with an
emphasis on optimization of topological ®t within the
binding site as well as incorporation of complementary
inhibitor±enzyme interactions. Based on initial model-
ing studies within the tetrahydrofolate cofactor binding
site, four inhibitors, 1±4, were pursued (Figure 2). Each
inhibitor retains the key hydrogen bond donor±accep-
tor±donor array across the upper face of the pyrimidine
ring which is suggested to represent a key factor in
cofactor binding and orientation through the formation
of hydrogen bonds with residues Arg-90 and Leu-92.4,5
An additional key feature is the replacement of the
cofactor formamide functionality by an aldehyde,
which renders the inhibitors unable to undergo formyl
In preceding studies,1 we detailed the preparation and
evaluation of potent inhibitors of glycinamide ribo-
nucleotide transformylase (GAR Tfase) and aminoimid-
azole carboxamide ribonucleotide transformylase
(AICAR Tfase), folate dependent enzymes responsible
for the transfer of a formyl group to GAR and AICAR
in the de novo synthesis of purines, based on the 5,8,10-
trideazafolate core. The most e€ective of the agents
incorporated a reactive, electrophilic group including a
nontransferable formyl group capable of reaction with
the nucleophilic amine of the enzymatic substrates GAR
and AICAR or active site residues of the enzymes
themselves. Herein, we detail the extension of these stu-
dies to the preparation and evaluation of 1±4 as poten-
tial antineoplastic agents and inhibitors of GAR Tfase
and AICAR Tfase (Figure 1).
Inhibitor Design
Key to the inhibitor design was the introduction of a
nontransferable formyl group potentially capable of
enzyme-assembled2 imine formation with the enzymatic
substrates.2,3 With the prospect of formation of an
enzyme-assembled tight binding inhibitor by virtue of
imine formation with GAR or AICAR, the objective
*Corresponding author. Tel: 619 784 7522; Fax: 619 784 7550.
0968-0896/98/$19.00 # 1998 Elsevier Science Ltd. All rights reserved
PII: S0968-0896(98)00040-6

644
D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
Figure 1.
Figure 2.
transfer. These compounds were designed to form a
tight binding ternary complex through enzyme-assisted
imine formation with the substrate GAR. In addition to
the pyrimidine hydrogen bonding array, inhibitor 1
incorporates the second ring across the bond adjacent to
that of the natural cofactor. This design ®lls an addi-
tional portion of the available hydrophobic space within
the binding pocket. The positioning of the side chain at
C-5 was found in modeling studies to overlap well with
the corresponding portion of the inhibitor 1476U89.4
The two inhibitors 3 and 4 represent even more simpli-
®ed analogues of which 4 possesses the additional cap-
ability of accommodating the Asp-144 backbone NH
hydrogen bond provided to the folate cofactor C4 car-
bonyl.
Chemistry
Inhibitor 2 incorporates the 5-deazapteridine ring sys-
tem, which is known to bind eciently within the
cofactor binding site (Figure 3).6 This compound incor-
porates the side chain at C-5 rather than at the C-6
position found in the natural cofactor and the classical
inhibitors including the clinical candidate DDATHF.6
Such folate analogues based on 5-deazapteridine sub-
stituted at C-5 have not previously been examined as
GAR Tfase inhibitors.
The initial stages of the synthesis of 2,4-diamino-5-(4-
oxobut-1-yl)quinazoline (1) followed well established
methodology for the construction of 2,4-diaminoquin-
azolines (Scheme 1).7 Commercially available 2-methyl-6-
nitroaniline (5) was converted to nitrile 6 via diazotiza-
tion and a subsequent Sandmeyer reaction. Reduction
of the nitro group with Fe±HOAc a€orded the aniline 7,
which was protected as the dibenzylamine 8. The side
chain was introduced by benzylic deprotonation and

D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
645
and 15 were converted to 1 by cleavage of the BOC
groups with tri¯uoroacetic acid in chloroform.
The direct reduction of 12 to the aldehyde 1 (DIBAL-H)
was unsuccessful due to the insolubility of 1 in the con-
ventional reaction medium (toluene). However, the ester
could be reduced to alcohol 16 with LiBH4 generated in
situ from NaBH4 and LiCl but 16 proved to be an
exceptionally insoluble solid (Scheme 2). As a con-
sequence of this insolubility, all attempts to e€ect its
oxidation were not as successful providing only trace
amounts of the desired aldehyde 1.
The successful approach to the synthesis of 2 utilized the
3-ethoxycarbonyl lactam 20 (Scheme 3). The precursor
to 20 was readily assembled by Michael addition of
diethyl malonate to the a,b-unsaturated nitrile 18
derived from a Horner±Emmons condensation of diethyl
cyanomethylphosphonate with the aldehyde 17. The
lactam was prepared from diester 19 by hydrogenation
reduction of the nitrile followed by cyclization. Thus,
hydrogenation of the nitrile 19 in acetic acid a€orded
the acetate salt of the product amine. Following
removal of the catalyst and solvent, heating the residue
under vacuum (0.1 mm Hg) at 160±170 ꢀC resulted in
cyclization to the lactam 20 with evolution of ethanol
and acetic acid. In contrast to related published proce-
Figure 3.
Michael addition to methyl acrylate. This reaction pro-
vided a mixture of the desired ester 9 and 10 resulting
from second reaction of 9 with methyl acrylate, as well
as recovered starting material (21%). Hydrogenolysis of
the benzyl protecting groups using Pearlman's catalyst
regenerated the free amine 11. Cyclization of 11 with
chloroformamidine hydrochloride8 produced the diamino-
quinazoline 12. Treatment of 12 with di-t-butyl dicar-
bonate and a catalytic amount of DMAP in the
presence of Et3N a€orded the tetra-(t-butyloxy-
carbonyl) derivative 13 which was found to be readily
soluble in the nonpolar media required for reduction to
the aldehyde. Reduction of 13 (2 equiv. DIBAL-H)
a€orded a mixture of aldehydes 14 (41%) and 15 (20%)
in which one of the BOC groups had been cleaved, as
well as unreacted starting material (25%). Aldehydes 14
9
dures which employ PtO2 and 60 psi H2 or Raney
Nickel at 100 atm H2,10 the reduction of 19 using PtO2
was found to proceed eciently at atmospheric pres-
sure. Treatment of the lactam with Me3OBF4 a€orded
the O-methyl lactam 21.
Neat condensation of lactam 21 with guanidine free
base,11 prepared from the hydrochloride and sodium 2-
ethoxyethoxide, resulted in formation of the tetra-
hydropyridopyrimidinone 22, completing the construc-
tion of the carbon framework for inhibitor 2.12 Cleavage
of the silyl protecting group a€orded alcohol 23 and an
important comparison sample for examination along-
side 2. The alcohol 23 was insoluble in most organic
solvents and this property precluded its direct oxidation
to 2. While the 1H NMR spectrum of 23 in CD3OD was
Scheme 1.
Scheme 2.

646
D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
Scheme 4.
Diels±Alder reaction of amidines with 2,4,6-tris(ethoxy-
carbonyl)-1,3,5-triazine (Scheme 5).14 Dealkylative
decarboxylation of 19 followed by closure of 32 to the
4-substituted piperidone 33 e€ected by hydrogenation
(1 atm) reduction of the nitrile and lactamization pro-
vided the key precursor to the requisite amidine 35.
Thermal reaction of the amidine with 2,4,6-tris(ethoxy-
carbonyl)-1,3,5-triazine (DMF, 90±110 ꢀC, 24±72 h)
provided only low conversions to the desired pyrimidine
36 and these results contrast the e€ective conversions
(75%) observed with the unsubstituted 2-iminopiper-
idine hydrochloride itself.14
Scheme 3.
clean, the 1H NMR spectrum in DMSO-d6 was complex
and the 13C NMR spectrum showed doubling of ®ve of
the 11 carbon resonances. Presumably, the pyrimidone
ring exists exclusively as the 4-keto tautomer in
CD3OD, while a mixture of the 4-keto and 4-hydroxy
tautomers is present in DMSO-d6.
The synthesis of the inhibitors 3 and 4 features more
successful applications of the inverse electron demand
Diels±Alder reaction of 2,4,6-tris(ethoxycarbonyl)-1,3,5-
triazine and amidine hydrochlorides for the construc-
tion of the substituted pyrimidines. Commercially
available 6-bromo-1-hexene was converted to the ami-
dine 39 via the nitrile 37 and intermediate imidate 38.
In order to increase the solubility of the alcohol prior to
oxidation, exhaustive carbamate formation with
BOC2O provided 24 of which one of the t-butyloxy-
carbonyl groups proved especially labile and could be
lost on simple storage to provide 25. Treatment of either
24 or 25 with Bu4NF served to deprotect the primary
alcohol cleanly providing 26 incorporating three t-butyl-
oxycarbonyl groups, two of which were spectro-
scopically identical. Dess±Martin oxidation13 of the
primary alcohol (3 equiv. o-Ph(CO2)I(OAc)3, CH2Cl2,
25 ꢀC, 2 h, 83%) followed by acid-catalyzed deprotec-
tion of 27 provided 2.
The latter stages of the preparation of 2 detailed above
proved superior to initial attempts employing the piva-
loylamide 28 where both the oxidation of 30 and the
®nal deprotection of 31 proved more problematic
(Scheme 4).
An interesting albeit less successful approach to 2 was
also examined based on the inverse electron demand
Scheme 5.

D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
647
Diels±Alder reaction of 39 a€ected by treatment with
2,4,6-tris(ethoxycarbonyl)-1,3,5-triazine provided the
pyrimidine 40 together with signi®cant amount of the
isomeric triazine 41 (Scheme 6). This latter unexpected
product represents the reaction of the C=NH double
bond of the amidine in the Diels±Alder reaction com-
petitive with the in situ amidine tautomerization to the
more reactive 1,1-diaminoethene. The best conversion
to 40 was observed when 2 equiv. of the triazine was
used and the amidine hydrochloride salt was added to
the reaction mixture every 4±6 h over a period of 24 h.
Direct ester hydrolysis of 40 (4 equiv. LiOH, THF±
CH3OH±H2O, 25 ꢀC, 2 h) followed by acidi®cation (pH
0±1) led to precipitation of the desired amino diacid 42
(95%). Curtius rearrangement on 42 followed by
exhaustive acylation with (BOC)2O provided 44.
.
Hydroboration of 44 e€ected with BH3 THF provided
45 (58%) and Dess±Martin oxidation a€orded 46 (89%).
Finally, acid-catalyzed BOC deprotection of 44±46
e€ected by tri¯uoroacetic acid (TFA) cleanly provided 3
and two comparison analogues 47 and 48.
In an analogous, but more e€ective sequence, the thio-
imidate 49 was converted to the potential inhibitor 4 and
its close comparison analogue 57 (Scheme 7). Inverse
electron demand Diels±Alder reaction of 49, derived
from acid-catalyzed addition of methanethiol to nitrile
37, with 2,4,6-tris(ethoxycarbonyl)-1,3,5-triazine cleanly
provided the pyrimidine 50 (63%) requiring preferential
loss of ammonia versus methanethiol from the [4+2]
cycloadduct. Ester hydrolysis (4 equiv. LiOH, THF±
CH3OH±H2O, 2 h, 25 ꢀC, 95%), Curtius rearrangement
(2.4 equiv. DPPA, 2.4 equiv. Et3N, 24 h, 85±95 ꢀC, 53±
67%), and exhaustive acylation with (BOC)2O provided
54. Hydroboration of 54 followed by Dess±Martin
oxidation of the resulting alcohol 55 provided the
aldehyde 56. Acid-catalyzed deprotection of 56 and 55
provided the key aldehyde 4 and a close comparison
analogue 57.
Scheme 6.
Inhibitor Studies
Interestingly, only 2 among the four aldehydes was
ine€ective against GART even though it most closely
embodies a cofactor analogue core characteristic of the
potent inhibitors disclosed to date. None of the agents
exhibited time-dependent inhibition consistent with
GAR imine formation and enzyme-catalyzed multi-
substrate adduct generation and inhibition. Thus,
although the inhibitor potency of 4 increased with time,
this time dependence was insensitive to preincubation
with or without GAR. Since preincubation with 10-
fDDAF partially protects inhibition with 4, this sug-
gests 4 acts as competitive inhibitor of the cofactor and
may slowly form a tighter binding hemiacetal enzyme
adduct.
The results of screening the various agents as enzyme
inhibitors against GAR Tfase and AICAR Tfase are
grouped in Tables 1±3. Thus, three of the four aldehydes
proved to be e€ective inhibitors of GAR Tfase (Ki 15±
40 mM) despite their simpli®ed structures and one, 3,
was also an inhibitor of AICAR Tfase. This is sig-
ni®cant given the simpli®ed nature of the inhibitors
which lack the entire benzoyl±glutamate side chain of
the natural cofactor and the potent enzyme inhibitors
disclosed to date. In the case of 1, the corresponding
alcohol and ester were ine€ective in inhibiting GAR
Tfase indicating that the non-transferable formyl group
is contributing signi®cantly to its properites (Table 1).

648
D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
Table 2. GAR and AICAR Tfase inhibitiona
Agent Ki GAR Tfase Ki AICAR Tfase
X
2
>100 mM
>100 mM
97‹5 mM
>100 mM
>100 mM
>100 mM
CHO
CH2OH
CH2OTBDPS
23
22
apurN GAR Tfase, avian AICAR Tfase.
Table 3. GAR and AICAR Tfase inhibitiona
Agent
Ki GAR Tfase
Ki AICAR Tfase
R
3
4
35‹2 mM
15‹2 mM
>100 mM
>100 mM
NH2
SMe
apurN GAR Tfase, avian AICAR Tfase.
Scheme 7.
the presence of purines. The aldehyde 1 and its com-
parison analogues 12 and 16 all exhibited comparable
cytotoxic activities and potencies in the presence or
absence of hypoxanthine (Table 4) illustrating that the
aldehyde of 1 did not enhance the potency or confer
selective GAR or AICAR Tfase inhibiting activity to
the agent. In addition, the potent activity of 1 does not
appear to be derived from selective inhibition of the de
novo synthesis of purines including its inhibition of
GAR or AICAR Tfase. This is perhaps not surprising
since the concentrations of 12 and 16 required for inhi-
bition of cell growth are well below that required for
detection of the inhibition of GAR Tfase and AICAR
Tfase and that of 1 is at least an order of magnitude
below the enzymatic Ki's.
In Vitro Cytotoxic Activity
The aldehydes 1 and 2 along with the comparison ana-
logues 12 and 16 or 22 and 23 were tested for cytotoxic
activity in the CCRF±CEM and L1210 cell lines both in
the absence (±) and presence (+) of hypoxanthine,
Tables 4 and 5. Thus, the cells were cultured in RPMI
1640 medium using dialyzed FBS for assessment of the
activity in the absence of purines and similarly cultured
with added 50 mM hypoxanthine for its assessment in
Table 1. GAR and AICAR Tfase inhibitiona
Examination of 1, 12, and 16 in an even broader range
of cell lines (A-549, BT-549, CAPAN-1, HT-29, MOLT-
4, NHDF, OVCAR-3, UCLA-P3, SIHA, SK-N-SH,
786-0, SK-MEL-28, RPMI-7666) revealed comparable
cytotoxic potencies to those listed in Table 4 (1±80 mM)
and did not reveal selected cytotoxic activity or a sensi-
tivity in the absence of purines or hypoxanthine.
Agent
Ki GAR Tfase
Ki AICAR Tfase
X
1
39.5‹0.5 mM
>100 mM
>100 mM
>100 mM
>100 mM
>100 mM
CHO
CH2Me
CH2OH
12
16
The aldehyde 2 and its comparison analogue 23 proved
to be less e€ective. Although 2 proved to be 5±10 times
apurN GAR Tfase, avian AICAR Tfase.

D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
Table 5. Cytotoxic activity (IC50, mM)a
649
more potent than 23, both were insensitive to the
absence or presence of purines. Thus, the activity
observed with 2 and 23 does not appear to be related to
the inhibition of de novo purine synthesis including the
inhibition of GAR or AICAR Tfase. In contrast to
expectations, the TBDPS ether 22 was found to be a
potent cytotoxic agent 10±100 times more potent than 2,
albeit insensitive to the presence or absence of medium
hypoxanthine.
Agent
L1210
CCRF-CEM
2 X=CHO
23 X=CH2OH
22 X=CH2OTBDPS
80,85
520,840
2,3
140,140
>100, >100
4,4
The results of the evaluation of 3 and 4 along with the
comparison agents 47±48 and 53/57 are provided in
Table 6. Although 3 consistently provided a three- to
fourfold cytotoxicity sensitivity when tested in the
absence of medium purines, it proved to be a relative
nonpotent agent. Both 48 and especially 47, which lack
the aldehyde, were more potent. Although the aldehyde
4 was found to be 5±10 times more potent than 3, it
exhibited no cytotoxicity sensitivity to the presence or
absence of medium purines, and proved to be only
slightly more potent or comparable to 53 and 57.
aDialyzed FBS: hypoxanthine, + hypoxanthine.
yellow needles. The mother liquor was puri®ed by ¯ash
chromatography (30% EtOAc±hexane) to a€ord a fur-
ther 2.95 g (28%, 81% total) of 6: mp 108±110 ꢀC (lit.7
mp 108±109 ꢀC); 1H NMR (CDCl3, 250 MHz) d 8.12
(m, 1H, C6-H), 7.65±7.69 (m, 2H), 2.69 (s, 3H, CH3); IR
(®lm) nmax 2221, 1531, 1457, 1344, 1300, 1196, 911, 808,
1
739 cm
;
FABHRMS (NBA±NaI) m/z 185.0321
(M++Na, C8H6N2O2 requires 185.0327).
Experimental
2-Cyano-3-methyl-nitrobenzene (6). A solution of 5 (10 g,
65.7 mmol) in glacial HOAc (25 mL) was treated with
6 M HCl (24 mL). The resulting suspension was cooled
to 10 ꢀC and treated with a solution of NaNO2 (5.55 g,
80.4 mmol) in H2O (18 mL) and the orange solution was
stirred for 30 min. A suspension of CuCl (8.07 g,
8.15 mmol) in H2O (50 mL) was treated with NaCN
(10.5 g, 214.2 mmol) forming a homogeneous solution,
followed by the addition of C6H6 (80 mL). The solution
containing the diazonium salt was added to the CuCN
solution and the resulting mixture was stirred at 25 ꢀC
for 1 h and warmed at 70±75 ꢀC for 1 h. The mixture
was ®ltered and the layers separated. The aqueous layer
was extracted with C6H6 (2Â40 mL) and the combined
organic layers were dried (MgSO4) and concentrated.
Crystallization (EtOH±H2O) a€orded 6 (5.60 g, 53%) as
2-Cyano-3-methylaniline (7). A suspension of 6 (8.0 g,
49 mmol) in 50% aqueous HOAc (300 mL) was heated
to 55±60 ꢀC until complete dissolution occurred. Iron
powder (27.2 g, 487 mmol) was added in portions at
such a rate as to just maintain re¯ux (ca. 30 min). After
the addition was complete, the mixture was warmed at
re¯ux for a further 15 min, then allowed to cool. The
suspension was ®ltered, the ®ltrate was added to H2O
(1000 mL) and extracted with EtOAc (3Â500 mL). The
combined extracts were washed with saturated aqueous
NaHCO3 to neutrality, dried (Na2SO4) and concen-
trated. Chromatography (30% EtOAc±hexane) a€orded
Table 6. Cytotoxic activity (IC50, mM)a
Table 4. Cytotoxic activity (IC50, mM)a
Agent
L1210
CCRF-CEM
R=NH2
3 X=CH2CHO
48 X=CH2CH2OH
47 X=CH=CH2
R=SMe
220, 930
120, 200
7,13
450, 1500
210, 240
20, 45
Agent
L1210
CCRF-CEM
1 X=CHO
12 X=CO2Me
16 X=CH2OH
2,3
2,4
1,1
2,3
23,18
9,10
4 X=CH2CHO
57 X=CH2CH2OH
53 X=CH=CH2
40, 25
90, 150
50, 70
25, 25
140, 170
100, 110
aDialyzed FBS: hypoxanthine, + hypoxanthine.
aDialyzed FBS: hypoxanthine, + hypoxanthine.

650
D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
7 (6.17 g, 6.52 g theoretical, 95%) as a yellow solid:
mp 24±126 ꢀC (EtOAc±hexane, yellow crystals) (lit.7
2H, C2-H), 1.98 (p, J=7.5 Hz, 2H); 13C NMR (CDCl3,
62.5 MHz) d 173.2, 154.9, 147.1, 137.0, 132.5, 128.2,
127.1, 122.6, 119.5, 117.3, 107.4, 56.6, 51.4, 33.8, 25.5;
IR (®lm) nmax 3061, 3021, 2941, 2842, 2214, 1734, 1585,
1575, 1361, 738, 699 cm 1; FABHRMS (NBA) m/z
399.2076 (M++H, C26H26N2O2 requires 399.2073).
Anal. calcd for C26H26N2O2: C, 78.36; H, 6.58; N, 7.03.
Found: C, 78.20; H, 6.46; N, 7.21.
mp 127±128 ꢀC); H NMR (CDCl3, 250 MHz) d 7.19 (t,
1
J=7.9 Hz, 1H, C5-H), 6.54±6.62 (m, 2H, C4-H, C6-H),
4.37 (br, 2H, NH2), 2.44 (s, 3H, CH3); IR (®lm) nmax
3395, 3333, 3231, 2205, 1646, 1595, 1574, 1472, 1297,
1
780 cm
;
FABHRMS (NBA±NaI) m/z 133.0760
(M++H, C8H8N2 requires 133.0766).
1
N,N-Dibenzyl-2-cyano-3-methylaniline (8). Potassium
hydride (35 wt%, 5.0 g, 43.6 mmol) was suspended in
anhydrous THF (40 mL) at 25 ꢀC. A solution of 7 (2.5 g,
18.9 mmol) in THF (20 mL) was added and the resulting
thick yellow precipitate was cooled to 0 ꢀC. Benzyl bro-
mide (10.6 mL, 89.1 mmol) was added over 10 min. The
suspension was warmed to 25 ꢀC and stirred for 5 h. The
mixture was quenched by the addition of saturated
aqueous NH4Cl (75 mL) and H2O (75 mL). The mixture
was extracted with CH2Cl2 (3Â100 mL) and the combined
organic layers dried (MgSO4) and concentrated. Chro-
matography (2±10% EtOAc±hexane, gradient elution)
a€orded 8 (5.87 g, 5.91 g theoretical, 99%) as a yellow
solid: mp 77±78 ꢀC; 1H NMR (CDCl3, 250 MHz) d
7.18±7.27 (m, 11H, phenyl, C5-H), 6.85 (d, J=7.4 Hz,
1H, C4-H), 6.76 (d, J=8.3 Hz, 1H, C6-H), 4.34 (s, 4H,
PhCH2), 2.52 (s, 3H, CH3); 13C NMR (CDCl3,
62.5 MHz) d 154.8, 143.9, 137.3, 132.4, 128.3, 127.2,
123.4, 119.0, 117.7, 107.8, 56.7, 21.0; IR (®lm) nmax
For 10: yellow oil; H NMR (CDCl3, 250 MHz) d 7.18±
7.30 (m, 11H), 6.84 (d, J=7.5 Hz, 1H, C6-H), 6.79 (d,
J=8.2 Hz, 1H, C4-H), 4.33 (s, 4H, PhCH2), 3.68 (s, 3H,
CH3), 3.64 (s, 3H, CH3), 2.81 (t, J=8.0 Hz, 2H), 2.42±
2.53 (m, 1H), 2.34 (dt, J=7.6, 2.7 Hz, 2H), 1.78±2.08
(m, 4H); 13C NMR (CDCl3, 62.5 MHz) d 175.2, 173.2,
155.0, 147.1, 137.1, 132.6, 128.3 (2C), 127.2, 122.6,
119.6, 117.3, 107.3, 56.7, 51.7, 51.5, 44.1, 32.8, 32.5,
26.9; IR (®lm) nmax 3061, 3031, 2941, 2852, 2214, 1729,
1585, 1575, 1495, 1470, 1450, 1241, 1201, 1162, 743,
1
699 cm
;
FABHRMS (NBA±NaI) m/z 507.2241
(M++Na, C30H32N2O4 requires 507.2260).
Methyl 4-(3-amino-2-cyanophenyl)butanoate (11). A
solution of 9 (1.51 g, 3.79 mmol) in glacial HOAc
(65 mL) was hydrogenated over a catalytic amount of
moist Pd(OH)2-C at 25 ꢀC under 1 atm H2. After 22 h,
the mixture was ®ltered through Celite, and rinsed with
H2O (200 mL) and EtOAc (300 mL). The layers were
separated and the aqueous layer was further extracted
with EtOAc (200 mL). The combined organic layers
were washed with saturated aqueous NaHCO3 to neu-
trality, then with H2O (250 mL), dried (Na2SO4) and
concentrated to a€ord 11 (683 mg, 827 mg theoretical,
3395, 3333, 3231, 2205, 1646, 1595, 1574, 1472, 1297,
1
780 cm
;
FABHRMS (NBA±NaI) m/z 335.1540
(M++Na, C22H20N2 requires 335.1524). Anal. calcd
for C22H20N2: C, 84.58; H, 6.45; N, 8.97. Found: C,
84.60; H, 6.29; N, 8.86.
1
83%) as an orange oil: H NMR (CDCl3, 250 MHz) d
Methyl 4-(3-dibenzylamino-2-cyanophenyl)butanoate (9)
and dimethyl 2-(2-(3-dibenzylamino-2-cyanophenyl)ethyl)
pentanedioate (10). A solution of diisopropylamine
(2.0 mL, 14.3 mmol) in anhydrous THF (20 mL) cooled
to 20 ꢀC was treated with n-BuLi (6.2 mL, 2.3 M in
hexane, 14.3 mmol) and the resulting solution was stirred
for 20 min before being cooled to 78 ꢀC. A solution of
8 (4.0 g, 12.8 mmol) in THF (12 mL) was added and the
deep red solution was stirred for 45 min at 78 ꢀC.
Methyl acrylate (1.3 mL, 14.4 mmol) was added and the
mixture was stirred for 15 min before being quenched by
the addition of saturated aqueous NH4Cl (25 mL). The
mixture was diluted with H2O (100 mL) and extracted
with CH2Cl2 (3Â100 mL). The combined organic layers
were dried (MgSO4) and concentrated. Chromatography
(20% EtOAc±hexane) a€orded 9 (1.95 g, 38%) and 10
(929 mg, 15%), as well as recovered 8 (840 mg, 21%).
7.12 (t, J=7.9 Hz, 1H, Ar C5-H), 6.54 (d, J=8.3 Hz,
1H, Ar C6-H), 6.48 (d, J=7.5 Hz, 1H, Ar C4-H), 4.59
(br s, 2H, NH2), 3.59 (s, 3H, CH3), 2.67 (t, J=7.6 Hz,
2H, C4-H), 2.28 (t, J=7.4 Hz, 2H, C2-H), 1.89 (p,
J=7.5 Hz, 2H, C3-H); 13C NMR (CDCl3, 62.5 MHz) d
173.3, 150.3, 145.0, 133.1, 117.6, 116.6, 112.5, 95.8, 51.2,
33.5, 32.8, 25.2; IR (®lm) nmax 3459, 3369, 3240, 2941,
2862, 2204, 1729, 1629, 1595, 1580, 1475, 1435, 788,
1
738 cm
;
FABHRMS (NBA±NaI) m/z 241.0949
(M++Na, C12H14N2O2 requires 241.0953).
2,4-Diamino-5-(3-methoxycarbonylprop-1-yl)quinazoline
(12). A mixture of 11 (303.8 mg, 1.39 mmol) and chloro-
formamidine hydrochloride8 (292 mg, 2.54 mmol) in
freshly distilled diglyme (7 mL) was warmed at 135 ꢀC
for 19 h. After cooling to 25 ꢀC, the solvent was removed
in vacuo. The residue was dissolved in H2O (15 mL) and
saturated aqueous NaHCO3 was added to neutrality.
The precipitated product was extracted into EtOAc
(2Â15 mL) and the organic phase dried (Na2SO4) and
concentrated. Chromatography (85:15:1 CHCl3±EtOH±
Et3N) a€orded 12 (274 mg, 362 mg theoretical, 76%) as
1
For 9: yellow oil; H NMR (CDCl3, 250 MHz) d 7.13±
7.25 (m, 11H), 6.82 (d, J=7.5 Hz, 1H, C6-H), 6.77 (d,
J=8.2 Hz, 1H, C4-H), 4.30 (s, 4H, PhCH2), 3.61 (s, 3H,
CH3), 2.83 (t, J=7.7 Hz, 2H, C4-H), 2.34 (t, J=7.4 Hz,

D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
651
a pale-yellow solid: mp 161±164 ꢀC (EtOAc±hexane, white
powder); 1H NMR (CF3CO2D, 400 MHz) d 7.87 (t,
J=8.0 Hz, 1H, C7-H), 7.42 (t, J=7.2 Hz, 2H, C6 and
C8-H), 3.75 (s, 3H, CH3), 3.09±3.14 (m, 2H, C10-H), 2.64
J=7.3 Hz, 2H, C30-H), 2.01 (p, J=7.6 Hz, 2H, C20-H),
1.44 (s, 18H, t-Bu), 1.32 (s, 18H, t-Bu); 13C NMR
(CDCl3, 62.5 MHz) d 201.4, 160.1, 155.2, 153.5, 150.7,
150.1, 138.4, 133.7, 130.0, 127.8, 119.8, 84.2, 83.3, 43.6,
33.7, 27.9, 27.6, 23.3; IR (®lm) nmax 2980, 2933, 1793,
(t, J=5.9 Hz, 2H, C30-H), 1.91±1.98 (m, 2H, C20-H); 13
C
NMR (CF3CO2D, 100 MHz) d 180.6, 160.2, 150.6,
146.1, 142.1, 141.5, 133.4, 119.4, 108.7, 54.6, 36.4, 33.7,
26.9; IR (KBr) nmax 3461, 3324, 3162, 2945, 1719, 1637,
1603, 1573, 1554, 1507, 1473, 1393, 1369, 1265, 1224,
1199, 1151, 1042, 985, 814 cm 1; FABHRMS (NBA±
CsI) m/z 393.0328 (M++Cs, C13H16N4O2 requires
393.0328). Anal. calcd for C13H16N4O2: C, 59.99; H,
6.20; N, 21.52. Found: C, 59.77; H, 6.01; N, 21.06.
1762, 1718, 1560, 1369, 1276, 1251, 1156, 1119,
1
853 cm
;
FABHRMS (NBA±CsI) m/z 763.2314
(M++Cs, C32H46N4O9 requires 763.2319). For 15: color-
less oil; 1H NMR (CDCl3, 250 MHz)
9.78 (t,
d
J=1.2 Hz, 1H, CHO), 7.92 (dd, J=8.4, 0.9 Hz, 1H),
7.71 (dd, J=8.4, 7.2 Hz, 1H), 7.44 (br s, 1H, NH), 7.32
(d, J=7.2 Hz, 1H), 3.04 (t, J=7.9 Hz, 2H, C10-H), 2.53
(dt, J=7.3, 1.0 Hz, 2H, C30-H), 2.00 (p, J=7.6 Hz, 2H,
C20-H), 1.57 (s, 9H, t-Bu), 1.32 (s, 18H, t-Bu); IR (®lm)
nmax 2979, 2923, 1793, 1762, 1718, 1560, 1369, 1275,
1251, 1162, 1105, 854 cm 1; FABHRMS (NBA) m/z
531.2837 (M++H, C27H38N4O7 requires 531.2819).
N,N,N0,N0-Tetra(t-butyloxycarbonyl)-2,4-diamino-5-(3-
methoxycarbonyl-prop-1-yl)quinazoline (13). A solution
of 12 (20 mg, 0.077 mmol) in THF (0.5 mL) was treated
with di-t-butyl dicarbonate (88 mL, 0.39 mmol), Et3N
(54 mL, 0.39 mmol), and 4-dimethylaminopyridine
(DMAP, 2 mg, 0.016 mmol). The resulting solution was
stirred at 25 ꢀC for 1 h before it was concentrated.
Chromatography (50% EtOAc±hexane) a€orded 13
(45 mg, 51 mg theoretical, 89%) as a white solid: mp
2,4-Diamino-5-(4-oxobut-1-yl)quinazoline (1). A solution
of 14 (6.2 mg, 0.0098 mmol) in CHCl3 (90 mL) was trea-
ted with CF3CO2H (30 mL), and the resulting solution
stirred at 25 ꢀC for 2 h. The solvents were evaporated
and the residue triturated with EtOAc to a€ord 1
(2.6 mg, 4.5 mg theoretical, 57%) as a white solid: 1H
NMR (DMF±d7, 400 MHz) d 9.80 (s, 1H, CHO), 7.76
(t, J=7.8 Hz, 1H), 7.44 (d, J=8.3 Hz, 1H), 7.33 (d,
J=7.4 Hz, 1H), 3.22 (t, J=8.1 Hz, 2H, C10-H), 1.98 (p,
J=8.1 Hz, 2H, C20-H); 1H NMR (CD3OD, 400 MHz,
hemiacetal) d 7.65 (t, J=7.9 Hz, 1H, C7-H), 7.25 (d,
J=8.0 Hz, 2H, C5-H, C6-H), 4.60 (t, J=5.2 Hz, 1H,
C40-H), 3.14 (t, J=8.0 Hz, 2H, C10-H), 1.98 (p,
J=8.1 Hz, 2H, C20-H); 1H NMR (CF3COOD,
400 MHz) d 9.84 (s, 1H), 7.98 (t, J=8 Hz, 1H), 7.53 (d,
J=8.3 Hz, 1H), 7.51 (d, J=7.4 Hz, 1H), 3.16 (t,
J=8.8 Hz, 2H), 3.04 (t, J=6.0 Hz, 2H), 2.06 (m, 2H);
13C NMR (CF3COOD, 100 MHz) d 211.9, 160.3, 151.0,
146.3, 142.2, 141.6, 133.5, 119.5, 108.7, 44.1, 36.1, 24.6;
IR (KBr) nmax 3412, 1676, 1599, 1512, 1200, 1128, 915,
820 cm 1; FABHRMS (NBA) m/z 231.1245 (M++H,
C12H14N4O requires 231.1246). Similarly, 15 (2.2 mg,
0.0066 mmol) in 48 mL of 3:1 v/v CHCl3±CF3CO2H
a€orded 1 (1.5 mg, 1.9 mg theoretical, 79%).
132±133.5 ꢀC (EtOAc±hexane, white crystals); H NMR
1
(CDCl3, 400 MHz) d 7.91 (dd, J=8.4, 0.9 Hz, 1H), 7.78
(dd, J=8.3, 7.3 Hz, 1H, C7-H), 7.48 (d, J=7.2 Hz, 1H),
3.66 (s, 3H, CH3), 3.10 (t, J=7.9 Hz, 2H, C10-H), 2.36
(t, J=7.5 Hz, 2H, C30-H), 2.00 (p, J=7.7 Hz, 2H, C20-
H), 1.41 (s, 18H, t-Bu), 1.30 (s, 18H, t-Bu); 13C NMR
(CDCl3, 62.5 MHz) d 173.3, 160.1, 153.4, 150.7, 150.0,
138.4, 133.7, 129.9, 127.6, 119.8, 84.1, 83.3, 51.6, 33.7,
33.6, 27.8, 27.6, 26.0; IR (®lm) nmax 2960, 2947, 1790,
1751, 1734, 1564, 1364, 1277, 1251, 1154, 1118, 1097,
1
851, 780, 728 cm
; FABHRMS (NBA±NaI) m/z
661.3450 (M++H, C33H48N4O10 requires 661.3449).
Anal. calcd for C33H48N4O10: C, 59.99; H, 7.32; N, 8.48.
Found: C, 59.89; H, 7.53; N, 8.29.
N,N,N0,N0-Tetra(t-butyloxycarbonyl)-2,4-diamino-5-(4-
oxobut-1-yl)quinazoline (14) and N,N,N0-tris(t-butyloxy-
carbonyl)-2,4-diamino-5-(4-oxobut-1-yl)quinazoline (15).
A solution of 13 (25 mg, 0.038 mmol) in anhydrous
toluene (750 mL) at 78 ꢀC was treated with a solution
of DIBAL±H (40 mL, 1.0 M in hexanes, 0.040 mmol).
After 15 min, an additional 50 mL (0.050 mmol) of
DIBAL±H solution was added. After 15 min, the reac-
tion was quenched by addition of CH3OH (500 mL) and
allowed to warm to 25 ꢀC. The mixture was added to
H2O (10 mL) and extracted with EtOAc (3Â10 mL). The
combined organic extracts were dried (Na2SO4) and
concentrated. Chromatography (30% EtOAc±hexane)
a€orded 14 (9.7 mg, 41%) and 15 (4.0 mg, 20%), as well
2,4-Diamino-5-(4-hydroxybut-1-yl)quinazoline (16).
A
solution of 12 (50 mg, 0.19 mmol) in 3:2 v/v EtOH±THF
(3.0 mL) was treated with NaBH4 (36 mg, 0.95 mmol)
and LiCl (40 mg, 0.94 mmol) and the mixture was
warmed at 55 ꢀC for 18 h. The reaction was quenched by
addition of acetone (10 mL) and the solvents removed in
vacuo. The residue was suspended in EtOH and ®ltered
through Celite. The EtOH was removed in vacuo and
the residue puri®ed by ¯ash chromatography (8:2:0.5
EtOAc:CH3OH:Et3N) to a€ord 16 (39 mg, 45 mg theo-
retical, 88%) as a white solid: mp > 210 ꢀC (decomp.);
1H NMR (CD3OD, 400 MHz) d 7.45 (dd, J=8.3,
7.3 Hz, 1H, C7-H), 7.18 (dd, J=8.4, 1.1 Hz, 1H), 7.00
1
as recovered 13 (6.3 mg, 25%). For 14: colorless oil; H
NMR (CDCl3, 250 MHz) d 9.78 (s, 1H, CHO), 7.95 (d,
J=8.4 Hz, 1H), 7.81 (t, J=7.8 Hz, 1H, C7-H), 7.50 (d,
J=7.0 Hz, 1H), 3.12 (t, J=7.9 Hz, 2H, C10-H), 2.54 (t,

652
D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
(d, J=7.2 Hz, 1H), 3.61 (t, J=6.3 Hz, 2H, C40-H), 3.09
(br t, J=7.9 Hz, 2H, C10-H), 1.75±1.83 (m, 2H, C20-H),
1.64 (p, J=6.8 Hz, 2H, C30-H); 13C NMR (CD3OD,
100 MHz) d 164.7, 160.9, 155.1, 141.2, 133.7, 125.2,
123.8, 111.0, 62.2, 36.8, 32.9, 28.7; IR (KBr) nmax
3476, 3351, 3139, 2925, 1663, 1618, 1603, 1577, 1550,
1477, 1400, 1269, 1059, 975, 750 cm 1; FABHRMS
(NBA) m/z 233.1409 (M++H, C12H16N4O requires
233.1402).
(t, J=6.2 Hz, 2H, C7-H), 3.49 (d, J=7.0 Hz, 1H, C2-H),
2.54±2.65 (m, 2H, CH2CN), 2.38±2.45 (m, 1H, C3-H),
1.34±1.57 (m, 6H), 1.25 (t, J=7.1 Hz, 3H, CO2
CH2CH3), 1.03 (s, 9H, t-Bu); 13C NMR (CDCl3,
62.5 MHz) d 168.0, 167.7, 135.5, 133.9, 129.6, 127.6,
118.0, 63.4, 61.8, 61.7, 53.9, 34.9, 32.2, 30.9, 26.8, 23.0,
19.3, 19.2, 14.0; IR (neat) nmax 2933, 2859, 2246, 1744,
1732, 1472, 1428, 1390, 1370, 1304, 1177, 1154, 1112,
1030, 823, 743, 704 cm 1; FABHRMS (NBA±NaI) m/z
546.2637 (M++Na, C30H41NO5Si requires 546.2652).
Anal. calcd for C30H41NO5Si: C, 68.80; H, 7.89; N, 2.67.
Found: C, 68.89; H, 7.49; N, 2.86.
(E,Z)-7-(t-Butyldiphenylsilyloxy)-2-heptenenitrile (18). A
suspension of NaH (60% dispersion, 675 mg,
16.9 mmol) in anhydrous THF (75 mL) at 0 ꢀC was
treated with diethyl cyanomethylphosphonate (2.85 mL,
17.6 mmol). The resulting solution was stirred for
30 min and was followed by the addition of 17 (5.0 g,
14.7 mmol) in THF (25 mL). The mixture was stirred at
0 ꢀC for 1 h before being added to H2O (300 mL) and
extracted with Et2O (2Â150 mL). The combined organic
layers were washed with saturated aqueous NaCl
(100 mL), dried (MgSO4) and concentrated. Flash chro-
matography (10% EtOAc±hexane) a€orded 18 (4.40 g,
5.34 g theoretical, 82%) as a colorless oil judged to be a
4-(4-(t-Butyldiphenylsilyloxy)but-1-yl)-3-ethoxycarbonyl-
2-piperidone (20). A solution of 19 (718 mg, 1.37 mmol)
in glacial HOAc (85 mL) was hydrogenated over PtO2
(31 mg, 0.14 mmol) at 25 ꢀC under 1 atm H2 for 24 h.
The reaction mixture was ®ltered through Celite and the
solvent removed in vacuo. The residual yellow oil was
heated at 160 ꢀC under vacuum (0.1 mm Hg) for 1 h,
then allowed to cool. The brown oil was puri®ed by
chromatography (80% EtOAc±hexane) to a€ord 20
(463 mg, 660 mg theoretical, 70%) as a pale-yellow oil:
1H NMR (CDCl3, 250 MHz) d 7.61±7.65 (m, 4H, Ar),
7.32±7.41 (m, 6H, Ar), 6.07 (br s, 1H, NH), 4.20 (q,
J=7.1 Hz, 2H, CO2CH2CH3), 3.63 (t, J=6.1 Hz, 2H,
C40-H), 3.29±3.34 (m, 2H, C6-H), 3.03 (d, J=9.6 Hz,
1H, C3-H), 1.30±2.18 (m, 9H), 1.25 (t, J=7.1 Hz, 3H,
CO2CH2CH3), 1.02 (s, 9H, t-Bu); 13C NMR (CDCl3,
62.5 MHz) d 170.5, 168.5, 135.5, 133.9, 129.5, 127.5,
63.5, 61.2, 55.4, 40.7, 35.9, 33.7, 32.4, 26.8, 25.8, 22.5,
1
mixture of E and Z isomers (ca. 1:1 ratio by H NMR):
1H NMR (CDCl3, 400 MHz) d 7.62±7.65 (m, 8H, Ar),
7.34±7.44 (m, 12H, Ar), 6.66 (dt, J=16.3, 6.9 Hz, 1H,
C3-H E-isomer), 6.43 (dt, J=10.9, 7.7 Hz, 1H, C3-H, Z-
isomer), 5.28 (dt, J=10.9, 1.4 Hz, 1H, C2-H, Z-isomer),
5.26 (dt, J=16.3, 1.7 Hz, 1H, C2-H, E-isomer), 3.63±
3.67 (m, 4H, C7-H), 2.37±2.42 (m, 2H, C4-H, Z-isomer),
2.15±2.20 (m, 2H, C4-H, E-isomer), 1.50±1.58 (m, 8H,
C5 and C6-H), 1.04 (s, 18H, t-Bu); 13C NMR (CDCl3,
100 MHz) d 155.8, 154.9, 135.4, 133.74, 133.68, 129.6,
129.5, 127.6, 117.5, 115.9, 99.7, 99.5, 63.2, 63.1, 32.8,
19.1, 14.1; IR (neat) nmax 3210, 2933, 2851, 1733, 1672,
1
1487, 1467, 1421, 1251, 1153, 1108, 1036, 821, 703 cm
;
FABHRMS (NBA±CsI) m/z 614.1715 (M++Cs,
C28H39NO4Si requires 614.1703). Anal. calcd for
C28H39NO4Si: C, 69.82; H, 8.16; N, 2.91. Found: C,
69.69; H, 7.79; N, 3.05.
31.54, 31.48, 26.8, 24.5, 23.8, 19.1; IR (neat) nmax 2935,
1
2859, 2218, 1628, 1105, 822, 738, 700, 686 cm
;
FABHRMS (NBA±NaI) m/z 386.1902 (M++Na,
C23H29NO2Si requires 386.1916). Anal. calcd for
C23H29NO2Si: C, 75.98; H, 8.04; N, 3.85. Found: C,
76.06; H, 7.72; N, 4.03.
4-(4-(t-Butyldiphenylsilyloxy)but-1-yl)-3-ethoxycarbonyl-
2-methoxy-3,4,5,6-tetrahydropyridine (21). A solution of
20 (169 mg, 0.35 mmol) in anhydrous CH2Cl2 (13 mL) at
4 ꢀC was treated with Me3OBF4 (205 mg, 1.39 mmol)
and the resulting suspension was stirred at 4 ꢀC for
90 min, during which most of the suspended material
dissolved. The reaction was warmed to 25 ꢀC and stirred
for 1 h, then added to CH2Cl2 (25 mL). The solution was
washed with saturated aqueous NaHCO3 (25 mL) and
the aqueous phase back extracted with CH2Cl2
(2Â20 mL). The combined organic layers were washed
with H2O (25 mL) and saturated aqueous NaCl (25 mL),
dried (MgSO4) and concentrated to a€ord 21 (581 mg,
628 mg theoretical, 92%) as a colorless oil which was
used in the subsequent reaction without further puri-
®cation: 1H NMR (CDCl3, 250 MHz) d 7.62±7.66 (m,
4H, Ar), 7.32±7.43 (m, 6H, Ar), 4.17 (q, J=7.1 Hz, 2H,
CO2CH2CH3), 3.61±3.66 (m, 5H, C40-H, OCH3), 3.56
Ethyl 7-(t-butyldiphenylsilyloxy)-3-cyanomethyl-2-(ethoxy-
carbonyl)heptanoate (19). A neat mixture of diethyl
malonate (3.5 mL, 23.0 mmol) and 18 (4.20 g,
11.6 mmol) was treated with 1.62 M NaOEt in EtOH
(720 mL, 1.17 mmol) and the mixture was warmed at
65 ꢀC for 25 h. The mixture was neutralized by addition
of HOAc (67 mL), diluted with CH2Cl2 (80 mL) and
washed with H2O (80 mL). The aqueous layer was back
extracted with CH2Cl2 (2Â40 mL) and the combined
organic layers were washed with saturated aqueous
NaCl (80 mL), dried (MgSO4) and concentrated. Chro-
matography (15% EtOAc±hexane) a€orded 19 (4.90 g,
6.05 g theoretical, 81%) as a colorless oil: 1H NMR
(CDCl3, 400 MHz) d 7.62±7.65 (m, 4H, Ar), 7.34±7.43
(m, 6H, Ar), 4.19 (q, J=7.1 Hz, 4H, CO2CH2CH3), 3.64

D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
653
(m, 2H, C6-H), 2.88 (d, J=8.8 Hz, 1H, C3-H), 1.11±
1.77 (m, 9H), 1.24 (t, J=7.1 Hz, 3H, CO2CH2CH3), 1.03
(s, 9H, t-Bu); 13C NMR (CDCl3, 62.5 MHz) d 171.4,
158.7, 135.5, 133.9, 129.5, 127.5, 63.6, 61.0, 52.7, 50.6,
45.6, 35.9, 33.9, 32.5, 26.8, 26.2, 22.6, 19.1, 14.1; IR
34.3, 32.9 and 32.8, 28.3, 24.0, 23.0; IR (KBr) nmax 3415,
3345, 2933, 2851, 1628, 1541, 1457, 1349, 1316, 1039,
782 cm 1; FABHRMS (NBA) m/z 239.1512 (M++H,
C11H18N4O2 requires 239.1508).
(neat) nmax 2935, 2852, 1732, 1685, 1473, 1457, 1426,
2-N,N-Bis(t-butyloxycarbonyl)amino-5-(4-((t-butyldi-
phenylsilyl)oxy)but-1-yl)-3,8-di(t-butyloxycarbonyl)-4-
hydroxy-5,6,7,8-tetrahydropyrido[2,3-d]pyrimidine (24)
and 2-N,N-bis(t-butyloxycarbonyl)amino-5-(4-((t-butyldi-
phenylsilyl)oxy)but-1-yl)-4-hydroxy-3,8-di(t-butyloxy-
carbonyl)-5,6,7,8-tetrahydropyrido[2,3-d]pyrimidine (25).
A solution of 22 (7.0 mg, 15 mmol) in THF (500 mL)
was treated sequentially with DMAP (0.2 mg, 1.6 mmol),
BOC2O (17.2 mL, 75 mmol) and Et3N (10.5 mL, 75 mmol)
and the mixture was stirred at 25 ꢀC for 2 h. The solvent
was evaporated and the residual solid was puri®ed by
preparative centrifugal TLC (SiO2, 0.5 mm plate, 10±
50% EtOAc±hexane gradient elution) to a€ord 24
(6.8 mg, 11.4 mg theoretical, 60%) and 25 (2.7 mg,
10.1 mg theoretical, 27%). For 24: colorless ®lm; Rf 0.45
(SiO2, 20% EtOAc±hexane); 1H NMR (CDCl3,
400 MHz) d 7.65 (m, 4H), 7.38 (m, 6H), 3.96 (m, 1H),
3.64 (t, J=6.4 Hz, 2H), 3.51 (m, 1H), 1.93 (m, 1H), 1.79
(m, 1H), 1.60±1.30 (m, 6H), 1.51 (s, 9H), 1.49 (s, 9H),
1.42 (s, 18H), 1.03 (s, 10H); 13C NMR (CDCl3,
100 MHz) d 163.1, 160.7, 154.3, 152.9, 150.6, 149.1, 139.9,
135.5, 129.6, 127.6, 111.3, 84.6, 83.1, 82.6, 63.6, 41.4,
32.7, 32.3, 30.0, 28.1, 27.8, 27.5, 26.9, 24.8, 23.2, 19.2;
1
1307, 1229, 1151, 1105, 1033, 820, 737, 701, 613 cm
;
FABHRMS (NBA±NaI) m/z 496.2889 (M++H,
C29H41NO4Si requires 496.2883).
2-Amino-5-(4-(t-butyldiphenylsilyloxy)but-1-yl)-4-hydroxy-
5,6,7,8-tetrahydropyrido[2,3-d]pyrimidine (22). Sodium
metal (48 mg, 2.1 mmol) was dissolved in 600 mL of dis-
tilled 2-ethoxyethanol and the resulting solution was
added to a solution of guanidine hydrochloride (200 mg,
2.1 mmol) in 600 mL 2-ethoxyethanol using an addi-
tional 400 mL solvent to complete transfer and providing
a 1.3 M solution of guanidine free base. The guanidine
solution (1.17 mL, 1.52 mmol) was added to 21 (355 mg,
0.72 mmol) and the 2-ethoxyethanol removed in vacuo.
The mixture was warmed at 90 ꢀC for 16 h, during which
solidi®cation occurred. The solid was taken up in
CH2Cl2 (20 mL) and H2O (20 mL) and the aqueous
layer adjusted to neutrality with dilute aqueous HCl.
The layers were separated and the aqueous layer
extracted with CH2Cl2 (2Â10 mL). The combined
organic layers were dried (MgSO4) and concentrated.
Chromatography (5% CH3OH±CH2Cl2) a€orded 22
(219.1 mg, 341 mg theoretical, 64%) as a white solid: mp
184±185 ꢀC (EtOAc±hexane, white powder); 1H NMR
(CDCl3, 400 MHz) d 7.62±7.65 (m, 4H, Ar), 7.32±7.41
(m, 6H, Ar), 5.70 (br s, 2H, N2-H), 5.04 (br s, 1H, N8-
H), 3.63 (t, J=6.2 Hz, 2H, C40-H), 3.25±3.30 (m, 2H,
C7-H), 2.71 (m, 1H, C5-H), 1.17±1.81 (m, 8H), 1.01 (s,
9H, t-Bu); 13C NMR (CDCl3, 62.5 MHz) d 163.0, 159.6,
153.4, 135.6, 134.1, 129.5, 127.6, 89.6, 63.9, 36.9, 34.1,
32.7, 28.7, 26.9, 24.0, 23.3, 19.2; IR (®lm) nmax 3333,
IR (KBr) nmax 2922, 1732, 1634, 1562, 1366, 1306, 1153,
1
1111, 850, 702 cm
; FABHRMS (NBA±CsI) m/z
1009.3715 (M++Cs, C47H68N4O10Si requires 1009.3759).
For 25: colorless ®lm; 1H NMR (CDCl3, 400 MHz) d
7.65 (m, 4H), 7.38 (m, 6H), 3.70 (m, 1H), 3.63 (t,
J=6.4 Hz, 2H), 3.52 (m, 1H), 2.85 (m, 1H), 1.78±1.60
(m, 8H), 1.55 (s, 18H), 1.46 (s, 9H), 1.02 (s, 10H); 13C
NMR (CDCl3, 100 MHz) d 161.4, 154.7, 151.8, 149.2,
145.5, 135.6, 134.1, 129.5, 127.6, 108.9, 86.1, 81.3, 63.9,
42.8, 32.6, 32.3, 30.1, 28.2, 27.7, 26.9, 26.5, 23.3, 19.2.
3190, 2933, 2862, 1615, 1544, 1462, 1426, 1349, 1108,
1
703 cm
;
FABHRMS (NBA±CsI) m/z 609.1640
(M++Cs, C27H36N4O2Si requires 609.1662). Anal.
calcd for C27H36N4O2Si: C, 68.03; H, 7.61; N, 11.75.
Found: C, 67.87; H, 7.49; N, 12.00.
2 - N,N - Bis (t - butyloxycarbonyl) amino - 8 - (t - butyloxy-
carbonyl)-4-hydroxy-5-(4-hydroxybut-1-yl)-5,6,7,8-tetra-
hydropyrido[2,3-d]pyrimidine (26). A solution of 24
(6.8 mg, 7.8 mmol) in THF (500 mL) was treated with
Bu4NF (16 mL, 1.0 M in THF, 16 mmol) and the mixture
was stirred at 25 ꢀC for 3 h. The solvent was evaporated
and the residual solid was puri®ed by ¯ash chromato-
graphy (SiO2, 2±5% CH3OH±CH2Cl2 gradient elution) to
a€ord 26 (3.5 mg, 4.2 mg theoretical, 83%) as a colorless
2-Amino-4-hydroxy-5-(4-hydroxybut-1-yl)-5,6,7,8-tetra-
hydropyrido[2,3-d]pyrimidine (23). A solution of 22
(20 mg, 0.042 mmol) in THF (330 mL) was treated with
Bu4NF (1 M in THF, 85 mL, 0.085 mmol) and the mix-
ture stirred at 25 ꢀC for 18 h. The solvent was evapo-
rated and the residual solid dissolved in 20% EtOH±
CHCl3. Chromatography (20% EtOH±CHCl3) a€orded
pure 23 (10.0 mg, 10.0 mg theoretical, 100%) as a white
1
thin ®lm: Rf 0.3 (SiO2, 5% CH3OH±CH2Cl2); H NMR
(CDCl3, 400 MHz) d 3.70 (m, 1H), 3.56 (m, 2H), 3.48
(m, 1H), 2.82 (m, 1H), 2.03±1.50 (m, 8H), 1.47 (s, 18H),
1.46 (s, 9H); 13C NMR (CDCl3, 100 MHz) d 161.7,
154.9, 151.8, 149.1, 145.5, 108.7, 86.0, 81.4, 62.8, 42.8,
32.5, 32.3, 29.8, 28.1, 27.7, 26.7, 23.2; IR (KBr) nmax
2932, 1800, 1723, 1641, 1564, 1469, 1366, 1314, 1254,
solid: mp 228±231 ꢀC; H NMR (CD3OD, 400 MHz) d
1
3.55 (t, J=6.4 Hz, 2H, C40-H), 2.79 (m, 1H, C5-H),
1.24±1.89 (m, 8H, C7-H obscured by solvent at 3.30);
13C NMR (DMSO-d6, 100 MHz) d 161.1, 158.9 and
158.8, 153.1, 87.5 and 87.4, 60.8 and 60.7, 35.9 and 35.8,

654
D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
1154, 1109, 1060 cm 1; FABHRMS (NBA±CsI) m/z
H), 3.26±3.29 (m, 2H, C7-H), 2.89 (m, 1H, C5-H), 1.18±
1.85 (m, 8H), 1.26 (s, 9H, t-Bu), 1.01 (s, 9H, t-Bu); 13C
NMR (CDCl3, 62.5 MHz) d 179.5, 160.0, 157.2, 147.9,
135.5, 134.1, 129.4, 127.4, 95.1, 64.0, 40.1, 37.0, 33.8,
32.7, 28.7, 27.0, 26.8, 23.6, 23.1, 19.2; IR (®lm) nmax
671.2026 (M++Cs, C26H42N4O8 requires 671.2057).
2-N,N-Bis(t-butyloxycarbonyl)amino-8-(t-butyloxycarb-
onyl)-4-hydroxy-5-(4-oxobut-1-yl)-5,6,7,8-tetrahydropyr-
ido[2,3-d]pyrimidine (27). A solution of 26 (3.5 mg,
6.5 mmol) in CH2Cl2 (200 mL) was treated with the Dess±
Martin periodinane13 (o-Ph(CO2)I(OAc)3, 7.0 mg,
17 mmol) and the mixture was stirred at 25 ꢀC for 2 h.
The solvent was evaporated and the residual solid was
puri®ed by ¯ash chromatography (SiO2, 50% EtOAc±
hexane) to a€ord 27 (2.9 mg, 3.5 mg theoretical, 83%) as
a colorless ®lm: Rf 0.35 (SiO2, 50% EtOAc±hexane); 1H
NMR (CDCl3, 400 MHz) d 9.75 (t, J=1.5 Hz, 1H), 3.74
(m, 1H), 3.52 (m, 1H), 2.87 (m, 1H), 2.48 (m, 2H), 1.78
(m, 4H), 1.24 (m, 2H); 13C NMR (CDCl3, 100 MHz) d
202.7, 161.4, 154.9, 151.7, 149.1, 145.7, 108.1, 86.2, 81.4,
43.8, 42.8, 36.2, 29.9, 28.2, 27.7, 26.6, 19.5; IR (KBr)
nmax 2975, 2928, 1806, 1774, 1722, 1637, 1562, 1365,
1308, 1276, 1252, 1153, 1121, 979, 853 cm 1; FABHRMS
(NBA±CsI) m/z 699.1870 (M++Cs, C26H40N4O8
requires 669.1900).
3374, 3262, 2931, 2857, 1640, 1610, 1573, 1482, 1461,
1
1388, 1308, 1205, 1154, 1111, 822, 779, 738, 701 cm
;
FABHRMS (NBA±CsI) m/z 693.2258 (M++Cs,
C32H44N4O3Si requires 693.2237).
For 29: colorless oil; 1H NMR (CDCl3, 400 MHz) d
11.51 (br s, 1H, N3-H), 7.88 (br s, 1H, C2-NH), 7.62±
7.65 (m, 4H, Ar), 7.33±7.41 (m, 6H, Ar), 3.67 (dd,
J=8.7, 4.0 Hz, 1H, C7-H), 3.63 (t, J=6.4 Hz, 2H, C40-
H), 3.42 (m, 1H, C7-H), 2.86 (m, 1H, C5-H), 1.17±1.89
(m, 8H), 1.29 (s, 9H, t-Bu), 1.27 (s, 9H, t-Bu), 1.01 (s,
9H, t-Bu); 13C NMR (CDCl3, 62.5 MHz) d 185.2, 179.6,
160.8, 155.9, 146.6, 135.5, 134.1, 129.4, 127.5, 106.6,
63.8, 44.1, 42.9, 40.2, 32.9, 32.6, 30.5, 28.8, 27.7, 26.9,
26.8, 23.2, 19.2; IR (®lm) nmax 3204, 2948, 2931, 2858,
1635, 1609, 1568, 1480, 1403, 1316, 1261, 1188, 1144,
1111, 822, 796, 740 cm 1; FABHRMS (NBA±CsI) m/z
777.2847 (M++Cs, C37H52N4O4Si requires 777.2812).
2-Amino-4-hydroxy-5-(4-oxobut-1-yl)-5,6,7,8-tetrahydro-
pyrido[2,3-d]pyrimidine (2). A solution of 27 (2.4 mg,
4.5 mmol) in CH2Cl2 (200 mL) was treated with 4 N HCl±
EtOAc (1.0 mL) and the mixture was stirred at 25 ꢀC for
2 h. The solvent was evaporated to a€ord 2 (1.1 mg,
1.06 mg theoretical, 100%) as a light-yellow oil: 1H
NMR (CF3COOD, 400 MHz) d 9.73 (br s, 1H), 3.57 (m,
1H), 3.48 (dd, J=13.2, 10.4 Hz, 1H), 3.00 (br s, 1H),
1.85±1.47 (m, 8H); 13C NMR (CF3COOD, 100 MHz) d
213.0, 162.5, 154.1, 151.9, 91.8, 39.2, 34.5, 31.4, 29.7,
23.9, 20.5; IR (KBr) nmax 3397, 2937, 1688, 1643, 1438,
1353, 1203, 1138, 843, 803, 718 cm 1; FABHRMS
(NBA) m/z 237.1352 (M++H, C11H16N4O2 requires
237.1359).
2-(t-Butylcarbonyl)amino-4-hydroxy-5-(4-hydroxybut-
1-yl)-5,6,7,8-tetrahydropyrido[2,3-d]pyrimidine (30). A
solution of 28 (32.5 mg, 0.058 mmol) in THF (460 mL)
was treated with Bu4NF (1 M in THF, 120 mL,
0.12 mmol) and the mixture was stirred at 25 ꢀC for 16 h.
The solvent was evaporated and the residual solid dis-
solved in CH2Cl2 (10 mL) and washed with H2O
(10 mL). The organic layer was dried (MgSO4) and
concentrated. Chromatography (5% CH3OH±CH2Cl2)
a€orded 30 (17.6 mg, 18.7 mg theoretical, 94%) as a
white powder: mp 213±215 ꢀC; 1H NMR (CDCl3,
250 MHz) d 8.03 (br s, 1H, NH), 4.83 (br s, 1H, N8-H),
3.58±3.69 (m, 2H, C40-H), 3.30±3.37 (m, 2H, C7-H),
2.94 (m, 1H, C5-H), 1.30±1.84 (m, 8H), 1.26 (s, 9H,
t-Bu); 13C NMR (CD3OD, 100 MHz) d 182.7, 162.2,
160.7, 150.3, 94.5, 62.9, 41.3, 37.5, 35.0, 33.8, 30.1, 27.0,
24.5, 24.2; IR (®lm) nmax 3374, 3265, 2934, 2862, 1653,
1576, 1559, 1540, 1457, 1349, 1313, 1200, 1149, 780,
728 cm 1; FABHRMS (NBA) m/z 323.2075 (M++H,
C16H26N4O3 requires 323.2083).
2-(t-Butylcarbonyl)amino-5-(4-(t-butyldiphenylsilyloxy)
but-1-yl)-4-hydroxy-5,6,7,8-tetrahydropyrido[2,3-d]pyrimi-
dine (28) and 8-(t-butylcarbonyl)-2-(t-butylcarbonyl)amino-
5-(4-(t-butyldiphenylsilyloxy)but-1-yl)-4-hydroxy-5,6,7,8-
tetrahydropyrido[2,3-d]pyrimidine (29). 4-Dimethylamino-
pyridine (2.5 mg, 0.020 mmol) and 22 (46.8 mg,
0.098 mmol) were combined in trimethylacetic anhydride
(330 mL) and the suspension was warmed at at 90 ꢀC
(complete solution occurred) for 6 h before being
allowed to stand at 25 ꢀC for 12 h. The mixture was
added to H2O (10mL) and extracted with CH2Cl2
(3Â10 mL). The combined organic layers were dried
(Na2SO4) and concentrated. Chromatography (30±50%
EtOAc±hexane gradient elution) a€orded 28 (32.5 mg,
59%) and 29 (12.6 mg, 19%). For 28: white powder, mp
187±189 ꢀC (EtOAc±hexane); 1H NMR (CDCl3,
250 MHz) d 7.62±7.66 (m, 4H, Ar), 7.31±7.42 (m, 6H,
Ar), 4.70 (br s, 1H, N8-H), 3.64 (t, J=6.2 Hz, 2H, C40-
2-(t-Butylcarbonyl)amino-4-hydroxy-5-(4-oxobut-1-yl)-
5,6,7,8-tetrahydropyrido[2,3-d]pyrimidine (31). A solu-
tion of oxalyl chloride (38 mL, 2.0 M in CH2Cl2,
0.076 mmol) in CH2Cl2 (100 mL) at 60 ꢀC was treated
with a solution of DMSO (11 mL, 0.155 mmol) in
CH2Cl2 (35 mL) and the resulting milky-white solution
was stirred for 10 min. A solution of 30 (7.9 mg,
0.025 mmol) in 1:1 v/v CH2Cl2±DMSO (150 mL) was
cooled to 23 ꢀC and added to the oxidant solution.
The mixture was warmed to 23 ꢀC and stirred for
15 min. Et3N (55 mL, 0.395 mmol) was added and the

D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
655
1
mixture stirred for 5 min, then allowed to warm to
1495, 1468, 1428, 1337, 1107, 820, 739, 700 cm
;
FABHRMS (NBA) m/z 410.2527 (M++H, C25H36
NO2Si requires 410.2512).
25 ꢀC. The mixture was added to H2O (5 mL) and
extracted with CH2Cl2 (3Â5 mL). The combined organic
layers were dried (Na2SO4) and concentrated. Chroma-
tography (5% CH3OH±CH2Cl2) a€orded 31 (2.1 mg,
7.8 mg theoretical, 27%) as a white solid: 1H NMR
(CDCl3, 400 MHz) d 9.75 (t, J=1.7 Hz, 1H, CHO), 4.83
(br s, 1H, N8-H), 3.29±3.32 (m, 2H, C7-H), 2.91 (m, 1H,
C5-H), 2.48 (m, 2H, C30-H), 1.18±1.90 (m, 6H), 1.26 (s,
9H, t-Bu); IR (®lm) nmax 3251, 2934, 2862, 1646, 1636,
1559, 1200, 1150 cm 1; FABHRMS (NBA±NaI) m/z
343.1731 (M++Na, C16H24N4O3 requires 343.1746).
4-(4-(t-Butyldiphenylsilyloxy)but-1-yl)-2-methoxy-3,4,5,6-
tetrahydropyridine (34). A solution of 33 (203 mg,
0.49 mmol) in anhydrous CH2Cl2 (4.8 mL) at 4 ꢀC was
treated with Me3OBF4 (81 mg, 0.55 mmol) and the
resulting suspension was stirred at 4 ꢀC for 2 h, during
which most of the suspended material dissolved. The
reaction was warmed to 25 ꢀC and stirred for 1 h before
being poured into saturated aqueous NaHCO3 (20 mL)
and extracted with CH2Cl2 (3Â20 mL). The combined
organic layers were washed with H2O (20 mL) and
saturated aqueous NaCl (20 mL), dried (Na2SO4) and
concentrated to a€ord 34 (200 mg, 210 mg theoretical,
95%) as a colorless oil which was used in the subsequent
reaction without further puri®cation: 1H NMR (CDCl3,
250 MHz) d 7.63±7.67 (m, 4H, Ar), 7.32±7.41 (m, 6H,
Ar), 3.65 (t, J=6.4 Hz, 2H, C40-H), 3.61 (s, 3H, OCH3),
3.29±3.42 (m, 2H, C6-H), 2.24 (dd, J=15.9, 3.8 Hz, 1H,
C3-H), 1.06±1.68 (m, 10H), 1.04 (s, 9H, t-Bu); IR (neat)
Ethyl 7-(t-butyldiphenylsilyloxy)-3-cyanomethylheptano-
ate (32). A solution of 19 (5.3 g, 10.1 mmol) in anhy-
drous DMSO (50 mL) was treated with anhydrous LiI
(10.6 g, 79.0 mmol) and the solution was warmed at
170 ꢀC for 2 h. The DMSO was removed under vacuum
and the residual oil was added to H2O (100 mL) and
extracted with CH2Cl2 (3Â50 mL). The combined
extracts were washed with saturated aqueous NaCl
(50 mL), dried (Na2SO4) and concentrated. Chromato-
graphy (15% EtOAc±hexane) a€orded 32 (3.06 g, 4.57 g
nmax 2931, 2857, 1683, 1472, 1428, 1216, 1111, 1008,
823, 740, 702, 614 cm
424.2660 (M++H, C26H38NO2Si requires 424.2672).
1
1
theoretical, 67%) as a colorless oil: H NMR (CDCl3,
;
FABHRMS (NBA) m/z
250 MHz) d 7.64±7.68 (m, 4H, Ar), 7.34±7.42 (m, 6H,
Ar), 4.14 (q, J=7.1 Hz, 2H, CO2CH2CH3), 3.67 (t,
J=6.1 Hz, 2H, C7-H), 2.46 (m, 2H, CH2CN), 2.40 (t,
J=6.4 Hz, 2H, C2-H), 2.17 (septet, J=6.2 Hz, 1H, C3-
H), 1.40±1.58 (m, 6H), 1.26 (t, J=7.1 Hz, 3H,
CO2CH2CH3), 1.05 (s, 9H, t-Bu); 13C NMR (CDCl3,
62.5 MHz) d 171.6, 135.5, 133.8, 129.5, 127.5, 118.0,
63.3, 60.6, 37.6, 33.0, 32.1, 31.8, 26.8, 22.8, 21.5, 19.1,
4-(4-(t-Butyldiphenylsilyloxy)but-1-yl)-2-iminopiperidine
hydrochloride (35).
A solution of 34 (189.6 mg,
0.45 mmol) in absolute EtOH (1 mL) was treated with
anhydrous NH4Cl (24.7 mg, 0.46 mmol) at 25 ꢀC for
24 h. The solvent was evaporated and the residue dis-
solved in Et2O (10 mL). Hexane (10 mL) was added and
the resulting precipitate collected by ®ltration to a€ord
35 (163 mg, 206 mg theoretical, 79%) as a hygroscopic
white solid: mp 121±123 ꢀC; 1H NMR (CDCl3,
250 MHz) d 10.01 (br s, 1H, NH), 8.94 (br s, 1H, NH),
7.61±7.65 (m, 4H, Ar), 7.29±7.44 (m, 6H, Ar), 3.64 (t,
J=6.1 Hz, 2H, C40-H), 3.47 (m, 1H, C6-H), 3.30 (dt,
J=11.9, 4.2 Hz, 1H, C6-H), 2.74 (dd, J=18.1, 3.9 Hz,
1H, C3-H), 2.16 (dd, J=18.1, 10.5 Hz, 1H, C3-H), 1.12±
1.92 (m, 9H), 1.02 (s, 9H, t-Bu); 13C NMR (CDCl3,
62.5 MHz) d 166.8, 135.5, 133.9, 129.6, 127.6, 63.4, 41.0,
34.7, 32.5, 32.3, 29.8, 26.8, 26.6, 22.5, 19.2; IR (®lm)
14.1; IR (neat) nmax 2931, 2851, 2236, 1734, 1458, 1427,
1
1374, 1256, 1174, 1111, 1026, 822, 702 cm
;
FABHRMS (NBA±NaI) m/z 474.2459 (M++Na,
C27H37NO3Si requires 474.2440). Anal. calcd for
C27H37NO3Si: C, 71.80; H, 8.26; N, 3.10. Found: C,
71.65; H, 8.51; N, 3.28.
4-(4-(t-Butyldiphenylsilyloxy)but-1-yl)-2-piperidone (33).
A solution of 32 (1.03 g, 2.28 mmol) in glacial HOAc
(145 mL) was hydrogenated over PtO2 (52 mg,
0.23 mmol) at 25 ꢀC under 1 atm H2 for 20 h. The reac-
tion mixture was ®ltered through Celite and the solvent
removed in vacuo. The residual yellow oil was heated at
170 ꢀC under vacuum (0.1 mm Hg) for 1 h, then allowed
to cool. The brown oil was puri®ed by ¯ash chromato-
graphy (5% EtOH±EtOAc) to a€ord 33 (890 mg,
934 mg theoretical, 95%) as a colorless oil: 1H NMR
(CDCl3, 250 MHz) d 7.62±7.66 (m, 4H, Ar), 7.32±7.44
(m, 6H, Ar), 5.85 (br s, 1H, NH), 3.64 (t, J=6.2 Hz, 2H,
C40-H), 3.24±3.32 (m, 2H, C6-H), 2.40 (ddd, J=17.3,
4.8, 1.8 Hz, 1H, C3-H), 1.21±1.98 (m, 10H), 1.03 (s, 9H,
t-Bu); 13C NMR (CDCl3, 62.5 MHz) d 172.2, 135.5,
133.9, 129.5, 127.5, 63.5, 41.1, 37.9, 35.3, 32.4, 28.1,
26.8, 22.7, 19.1; IR (neat) nmax 3221, 2924, 2858, 1663,
nmax 3436, 3354, 3190, 3138, 3067, 2933, 2851, 1687,
1
1646, 1462, 1420, 1344, 1185, 1092, 820, 692 cm
;
FABHRMS (NBA) m/z 409.2668 (M++H, C25H36
N2OSi requires 409.2675).
2,4-Bis(ethoxycarbonyl)-5-(4-(t-butyldiphenylsilyloxy)but-
1-yl)-5,6,7,8-tetrahydropyrido[2,3-d]pyrimidine (36). A
suspension of 35 (9.5 mg, 0.021 mmol) and 2,4,6-tris
(ethoxycarbonyl)-1,3,5-triazine14 (63 mg, 0.21 mmol) in
anhydrous DMF (50 mL) was warmed at 120 ꢀC for 36 h.
The solvent was removed in vacuo and the residue pur-
i®ed by ¯ash chromatography (1% CH3OH±CH2Cl2)
followed by PTLC (1% CH3OH±CH2Cl2) to a€ord 36

656
D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
(1.8 mg, 12.6 mg theoretical, 14%) as a yellow oil: 1H
NMR (CDCl3, 250 MHz) d 7.61±7.64 (m, 4H, Ar), 7.32±
7.43 (m, 6H, Ar), 6.12 (br s, 1H, NH), 4.44 (q,
J=7.1 Hz, 2H, C2-CO2CH2CH3), 4.37 and 4.38 (two q,
J=7.1 Hz, 2H, C4-CO2CH2CH3), 3.64 (t, J=5.6 Hz,
2H, C40-H), 3.42±3.46 (m, 3H, C5 and C7-H), 1.11±1.98
(m, 8H), 1.40 (t, J=7.1 Hz, 3H, CO2CH2CH3), 1.36 (t,
J=7.1 Hz, 3H, CO2CH2CH3), 1.02 (s, 9H, t-Bu); 13C
NMR (CDCl3, 100 MHz) d 164.8, 163.1, 160.1, 153.0,
151.4, 135.5, 134.7, 133.9, 129.6, 128.9, 127.5, 120.1,
63.5, 62.8, 62.3, 36.7, 33.3, 32.2, 30.9, 26.8, 22.7, 21.8,
(ddt, J=10.4, 1.9, 1.3 Hz, 2H), 2.35 (t, J=7.7 Hz, 2H),
2.03 (dt, J=7.3, 6.9 Hz, 2H), 1.59 (tt, J=8.0, 7.4 Hz,
2H), 1.35 (tt, J=7.7, 7.3 Hz, 2H); 13C NMR (CD3OD,
100 MHz) d 173.2, 139.2, 115.6, 34.2, 33.3, 29.2, 27.6; IR
(neat) nmax 3037, 2923, 1682, 1638, 1515, 1441, 1410,
1125, 994, 911 cm 1; FABHRMS (NBA) m/z 127.1238
(M++H, C7H14N2 requires 127.1235).
6-Amino-2,4-bis(ethoxycarbonyl)-5-(pent-4-en-1-yl)pyrimi-
dine (40). A solution of 2,4,6-tris(ethoxycarbonyl)-1,3,5-
triazine (2.56 g, 8.6 mmol) in anhydrous DMF (4 mL)
was warmed to 105 ꢀC and stirred under Ar. Samples of
39 (0.70 g, 4.3 mmol) was added in four portions every
5 h. After the ®nal addition, the solution was allowed to
stir at 105 ꢀC for 48 h before the solvent was removed in
vacuo. Flash chromatography (SiO2, 20±50% EtOAc±
hexane) followed by recrystallization from EtOAc±hex-
ane provided 40 (230 mg, 35%) as bright-yellow crystals:
Rf 0.28 (SiO2, 50% EtOAc±hexane); mp 171±172 ꢀC
(yellow plates, EtOAc±hexane); 1H NMR (CDCl3,
400 MHz) d 6.08 (br s, 2H), 5.82 (ddt, J=17.1, 10.3,
6.7 Hz, 1H), 5.08 (ddt, J=17.1, 1.7, 1.6 Hz, 1H), 5.04
(ddt, J=10.3, 1.8, 1.4 Hz, 1H), 4.46 (q, J=7.2 Hz, 2H),
4.42 (q, J=7.2 Hz, 2H), 2.65±2.61 (m, 2H), 2.15 (dt,
J=7.1, 6.9 Hz, 2H), 1.69 (tt, J=8.0, 7.3 Hz, 2H), 1.42 (t,
J=7.1 Hz, 3H), 1.41 (t, J=7.1 Hz, 3H); 13C NMR
(CDCl3, 100 MHz) d 165.3, 163.6, 163.3, 154.4, 153.9,
137.4, 118.6, 116.2, 62.7, 62.3, 33.4, 26.6, 25.7, 14.2,
14.1; IR (neat) nmax 3342, 3204, 2976, 2935, 1734, 1627,
1571, 1444, 1235, 1018 cm 1; FABHRMS (NBA±CsI)
m/z 440.0569 (M++Cs, C15H21N3O4 requires
440.0586).
19.2, 14.2, 14.1; IR (®lm) nmax 3259, 2931, 2858, 1735,
1
1596, 1334, 1246, 1210, 1188, 1111, 1023, 703 cm
;
FABHRMS (NBA±NaI) m/z 612.2842 (M++Na,
C33H43N3O5Si requires 612.2870).
Methyl hept-6-enimidate hydrochloride (38). A solution
of 37 (1.24 g, 11.4 mmol) in anhydrous CH3OH (0.37 g,
11.4 mmol) was treated with excess dry HCl gas at
75 ꢀC. The reaction mixture was slowly warmed to
25 ꢀC and stirred for 5 h. Anhydrous Et2O (20 mL) was
added at 40 ꢀC and the precipitate was collected by
®ltration under N2 and dried in vacuo to provide 38
(1.67 g, 83%) as white crystals: mp 79±80 ꢀC (sealed
1
tube); H NMR (CDCl3, 400 MHz) d 12.54 (br s, 1H),
11.59 (br s, 1H), 5.71 (ddt, J=17.1, 10.2, 6.7 Hz, 1H),
5.01 (ddt, J=17.1, 1.7, 1.6 Hz, 1H), 4.93 (ddt, J=10.3,
2.0, 1.1 Hz, 1H), 4.27 (s, 1H), 2.74 (t, J=7.7 Hz, 2H),
2.08 (dt, J=7.2, 7.2 Hz, 2H), 1.71 (tt, J=7.6, 7.8 Hz,
2H), 1.45 (tt, J=7.6, 7.4 Hz, 2H); 13C NMR (CDCl3,
100 MHz) d 180.1, 137.5, 115.2, 60.6, 32.8, 32.6, 27.7,
24.9; IR (neat) nmax 3402, 2924, 1661, 1641, 1472, 1402,
1198, 1098, 994, 909, 849, 815 cm 1; FABHRMS (NBA)
m/z 142.1238 (M++H, C8H15NO requires 142.1232).
2,4-Bis(ethoxycarbonyl)-6-methylthio-5-(pent-4-en-1-yl)
pyrimidine (50). Warming 49 for 24 h at 105 ꢀC follow-
ing the procedure detailed for 40 provided 50 (63%) as a
colorless oil: Rf 0.65 (SiO2, 50% EtOAc±hexane); 1H
NMR (CDCl3, 400 MHz) d 5.72 (ddt, J=10.2, 17.0,
6.6 Hz, 1H), 4.96 (ddt, J=1.6, 1.8, 17.0 Hz, 1H), 4.91
(ddt, J=2.1, 1.0, 9.1 Hz, 1H), 4.38 (q, J=7.2 Hz, 2H),
4.35 (q, J=7.2 Hz, 2H), 2.73±2.69 (m, 2H), 2.58 (s, 3H),
2.07 (dt, J=7.2, 6.9 Hz, 2H), 1.67±1.59 (m, 2H), 1.34 (t,
J=7.2 Hz, 3H), 1.32 (t, J=7.2 Hz, 3H); 13C NMR
(CDCl3, 100 MHz) d 173.2, 170.9, 164.7, 163.1, 153.4,
152.8, 137.3, 132.7, 115.4, 62.3, 60.2, 33.7, 27.9, 27.0,
13.9, 13.0; IR (neat) nmax 3077, 2980, 2933, 1733, 1641,
1540, 1463, 1381, 1306, 1239, 1184, 1132, 1020, 914, 892,
865, 833, 737 cm 1; FABHRMS (NBA) m/z 339.1369
(M++H, C16H22N2O4S requires 339.1379).
Methyl hept-6-enethioimidate hydrochloride (49). Treat-
ment of 37 with HCl and CH3SH following the same
procedure for 38 provided 49 (100%) as a thick yellow
oil: 1H NMR (DMSO-d6, 400 MHz) d 5.81±5.74 (m,
1H), 5.04±4.94 (m, 2H), 2.83 (t, J=7.6 Hz, 2H), 2.03 (dt,
J=6.8, 7.1 Hz, 2H), 1.68 (tt, J=7.7, 7.4 Hz, 2H), 1.39
(tt, J=7.6, 7.6 Hz, 2H); 13C NMR (CDCl3, 100 MHz) d
194.9, 136.7, 113.9, 36.1, 31.8, 27.1, 26.6, 15.1; IR (neat)
nmax 3405, 3067, 2852, 1831, 1636, 1544, 1462, 1421,
1
966, 909, 735 cm
; FABHRMS (NBA±CsI) m/z
158.1006 (M++H, C8H15NS requires 158.1003).
Hept-6-enamidine hydrochloride (39). A solution of 38
(0.80 g, 4.51 mmol) in anhydrous Et2O (4 mL) at 0 ꢀC
was treated with NH3 (8% in EtOH, 1.94 g, 9.13 mmol).
The reaction mixture was allowed to warm to 25 ꢀC and
stirred under Ar for 8 h. The solvent was then removed
under a mild stream of N2 to provide 39 (0.73 g, 100%)
6-Amino-5-(pent-4-en-1-yl)pyrimidine-2,4-dicarboxylic
acid hydrochloride (42). A solution of 40 (154 mg,
0.5 mmol) in THF:CH3OH:H2O (3:1:1, 20 mL) was
1
ꢀ
.
as a white semisolid: H NMR (DMSO-d6, 400 MHz) d
8.90 (br s, 2H), 8.52 (br s, 2H), 5.82 (ddt, J=17.0, 10.4,
6.6 Hz, 1H), 5.02 (ddt, J=17.0, 1.7, 1.7 Hz, 2H), 4.96
treated with LiOH H2O (84 mg, 2 mmol) at 25 C for
2 h. The solvent was removed in vacuo and redissolved
in H2O (1.5 mL). Aqueous 10% HCl was added drop-

D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
657
wise until the pH reached 0±1. The white precipitate was
collected by ®ltration, washed with H2O (2Â5 mL),
dried (MgSO4), and concentrated to provide 42 (120 mg,
95%) as an o€-white powder: mp 197±198 ꢀC (sealed
tube); 1H NMR (DMSO-d6, 400 MHz) d 7.40 (br s, 2H),
5.80 (ddt, J=17.2, 10.4, 6.4 Hz, 1H), 5.00 (ddt, J=17.2,
2.0, 1.4 Hz, 1H), 4.94 (ddt, J=10.4, 2.1, 1.2 Hz, 1H),
2.55 (t, J=8.0 Hz, 2H), 2.07 (dt, J=7.4, 7.0 Hz, 2H),
1.51 (tt, J=7.5, 7.5 Hz, 2H); 13C NMR (D2O, 100 MHz)
d 176.5, 173.7, 165.5, 163.5, 161.2, 141.6, 117.4, 114.8,
35.4, 28.8, 27.9; IR (KBr) nmax 3374, 3292, 3221, 2933,
(14%). For 52: colorless ®lm; Rf 0.25 (SiO2, 20%
1
EtOAc±hexane); H NMR (CDCl3, 400 MHz) d 8.13 (s,
1H), 5.78 (ddt, J=17.2, 10.3, 6.6 Hz, 1H), 5.05 (ddt,
J=15.6, 1.5, 1.8 Hz, 1H), 4.98±4.94 (m, 1H), 2.47 (s,
3H), 2.38 (t, J=5.7 Hz, 2H), 2.08 (dt, J=7.0, 6.8 Hz,
2H), 1.56 (tt, J=7.6, 7.6 Hz, 2H), 1.47 (s, 9H); 13C
NMR (CDCl3, 100 MHz) d 166.5, 160.5, 154.3, 151.2,
138.0, 115.3, 107.4, 80.9, 33.4, 28.2, 25.8, 25.4, 12.9; IR
(neat) nmax 3326, 3221, 2972, 2924, 1735, 1670, 1625,
1
1577, 1549, 1496, 1424, 1362, 1219, 1152 cm
;
FABHRMS (NBA) m/z 325.1689 (M++H, C15H24
N4O2S requires 325.1698).
1774, 1641, 1618, 1569, 1523, 1534, 1354, 1226, 1036,
1
918, 764 cm
; FABHRMS (NBA) m/z 252.0973
(M++H, C11H13N3O4 requires 252.0984).
For 53 (2,4-diamino-6-methylthio-5-(pent-4-en-1-yl)
pyrimidine): colorless ®lm; Rf 0.22 (SiO2, 50% EtOAc±
hexane); 1H NMR (CD3OD, 400 MHz) d 5.85 (ddt,
J=17.1, 10.3, 6.6 Hz, 1H), 5.02 (ddt, J=17.1, 1.8,
1.6 Hz, 1H), 4.93 (ddt, J=10.2, 2.1, 1.1 Hz, 1H), 2.41 (s,
3H), 2.40 (t, J=6.5 Hz, 2H), 2.11 (dt, J=7.0, 6.8 Hz,
2H), 1.56±1.52 (m, 2H); 13C NMR (CD3OD, 100 MHz)
d 167.5, 162.3, 161.9, 139.8, 115.1, 103.5, 34.8, 28.0,
6-Methylthio-5-(pent-4-en-1-yl)pyrimidine-2,4-dicarboxy-
lic acid (51). Following the procedure for the prepara-
tion of 42, 51 was prepared from 50. The white pre-
cipitate that appeared upon acidi®cation was dissolved
into EtOAc (2Â20 mL). The organic layers were com-
bined, washed with H2O (2Â5 mL), dried (MgSO4), and
concentrated to provide 51 (95%) as a white powder: 1H
NMR (CD3OD, 400 MHz) d 5.82 (ddt, J=10.0, 17.2,
6.4 Hz, 1H), 5.03 (ddt, J=1.5, 1.8, 16.8 Hz, 1H), 4.97
(ddt, J=2.1, 1.0, 9.5 Hz, 1H), 2.90±2.86 (m, 2H), 2.67 (s,
3H), 2.16 (dt, J=7.0, 6.8 Hz, 2H), 1.74±1.66 (m, 2H);
13C NMR (CD3OD, 100 MHz) d 175.5, 167.3, 166.1,
154.2, 153.6, 138.8, 134.4, 115.7, 35.0, 29.1, 28.2, 13.5;
IR (neat) nmax 3455, 2928, 1733, 1640, 1547, 1390, 1331,
1303, 1258, 1182, 1103, 991, 916 cm 1; FABHRMS
(NBA) m/z 283.0760 (M++H, C12H14N2O4S requires
283.0753).
26.2, 12.9; IR (neat) nmax 3460, 3319, 3178, 2925, 2850,
1
1605, 1544, 1422, 1347, 1258, 1103, 892 cm
;
FABHRMS (NBA) m/z 225.1169 (M++H, C10H16N4S
requires 225.1174).
2,4,6-Tris[N,N-bis(t-butyloxycarbonyl)amino]-5-(pent-4-
en-1-yl)pyrimidine (44).
A solution of 43 (54 mg,
0.19 mmol) in THF (5 mL) was treated with di-t-butyl
dicarbonate (255 mL, 1.11 mmol), DMAP, and Et3N
(154 mL, 1.11 mmol). The reaction mixture was stirred at
25 ꢀC for 2 h followed by removal of the solvent in
vacuo. Flash chromatography (SiO2, 10% EtOAc±hex-
ane) provided 44 (104 mg, 71%) as a colorless ®lm: Rf
0.35 (SiO2, 10% EtOAc±hexane); 1H NMR (CDCl3,
400 MHz) d 5.75 (ddt, J=17.0, 10.3, 6.4 Hz, 1H), 5.02
(ddt, J=17.0, 1.7, 1.6 Hz, 1H), 5.01±4.98 (m, 1H), 2.48±
2.41 (m, 2H), 2.08 (dt, J=7.2, 6.8 Hz, 2H), 1.62 (tt,
J=7.8, 7.9 Hz, 2H), 1.43 (s, 18H), 1.42 (s, 36H); 13C
NMR (CDCl3, 100 MHz) d 161.6, 155.9, 150.6, 150.0,
137.6, 128.2, 115.4, 83.9, 83.3, 33.7, 27.8, 27.7, 26.7,
26.0; IR (neat) nmax 2979, 2932, 1795, 1762, 1725, 1551,
1457, 1450, 1392, 1369, 1275, 1251, 1158, 1115, 1097,
848, 778 cm 1; FABHRMS (NBA±CsI) m/z 926.3550
(M++Cs, C39H63N5O12 requires 926.3528).
2-N-(t-Butyloxycarbonyl)amino-4,6-diamino-5-(pent-4-
A mixture of 42 (300 mg,
en-1-yl)pyrimidine (43).
1.2 mmol), powdered 4 A molecular sieves (20 mg), and
Et3N (500 mL, 3.6 mmol) in anhydrous t-BuOH
(100 mL), was treated dropwise with diphenylphos-
phoryl azide (DPPA, 773 mL, 3.6 mmol). The reaction
mixture was allowed to stir at 100 ꢀC for 72 h before the
solvent was removed in vacuo. Flash chromatography
(SiO2, 1±10% CH3OH±CH2Cl2) provided 43 (92 mg,
28%): Rf 0.28 (SiO2, 5% CH3OH±CH2Cl2); 1H NMR
(CDCl3, 400 MHz) d 5.80 (ddt, J=17.4, 10.4, 6.5 Hz,
1H), 5.09±5.00 (m, 2H), 2.30 (t, J=6.0 Hz, 2H), 2.13 (dt,
J=5.6, 5.6 Hz, 2H), 1.60 (tt, J=6.0, 6.3 Hz, 2H), 1.52 (s,
9H); 13C NMR (CDCl3, 100 MHz) d 160.2, 152.7, 151.6,
138.2, 115.7, 90.4, 82.1, 33.0, 28.3, 25.9, 23.0; IR (neat)
2,4-Bis[N,N-bis(t-butyloxycarbonyl)amino]-6-methylthio-
5-(pent-4-en-1-yl)pyrimidine (54). Following the proce-
dure for 44, 52 provided 54 (90%) as a colorless ®lm: Rf
0.35 (SiO2, 10% EtOAc±hexane); 1H NMR (CDCl3,
400 MHz) d 5.78 (ddt, J=17.1, 10.3, 6.6 Hz, 1H), 5.02
(ddt, J=17.1, 1.8, 1.6 Hz, 1H), 5.00±4.97 (m, 1H), 2.54
(s, 3H), 2.54±2.50 (m, 2H), 2.11 (dt, J=7.2, 7.0 Hz, 2H),
1.66±1.62 (m, 2H), 1.43 (s, 18H), 1.41 (s, 18H); 13C
NMR (CDCl3, 100 MHz) d 172.7, 156.6, 155.2, 150.8,
149.9, 137.6, 127.1, 115.3, 83.6, 83.1, 33.7, 28.0, 27.7,
nmax 3334, 3195, 2981, 2927, 2857, 1726, 1638, 1601,
1
1582, 1434, 1364, 1244, 1146, 1044, 915 cm
;
FABHRMS (NBA) m/z 294.1935 (M++H, C14H23
N5O2 requires 294.1930).
4-Amino-2-N-(t-butyloxycarbonyl)amino-6-methylthio-5-
(pent-4-en-1-yl) pyrimidine (52). Following the proce-
dure detailed for 43, 51 provided 52 (53%) and 53

658
D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
26.7, 26.0, 13.4; IR (neat) nmax 2979, 1797, 1762, 1730,
1560, 1530, 1458, 1394, 1368, 1275, 1253, 1156, 1117,
854, 777 cm 1; FABHRMS (NBA±CsI) m/z 757.2218
(M++Cs, C30H48N4O8S requires 757.2247).
2,4,6-Triamino-5-(5-hydroxypent-1-yl)pyrimidine (48). A
solution of 45 (16 mg, 20 mmol) in CH2Cl2 (0.5 mL) was
treated with tri¯uoroacetic aicd (0.2 mL) at 25 ꢀC for
2 h. The solvent was removed in vacuo. The residue was
redissolved in THF:CH3OH:H2O (3:1:1, 0.2 mL) and
.
treated with LiOH H2O (4.2 mg, 0.1 mmol) for 1 h. The
5-(Pent-4-en-1-yl)-2,4,6-triaminopyrimidine tri¯uoro-
solution of 44 (19.2 mg,
acetic acid salt (47).
A
solvent was removed in vacuo and the reaction mixture
was extracted with EtOAc (3Â5 mL). The organic layers
were combined, washed with saturated aqueous NaCl
(1 mL), H2O (1 mL), dried (MgSO4) and concentrated to
provide 48 (3.6 mg, 85%) as an o€-white ®lm: Rf 0.25
(SiO2, 10% CH3OH±CH2Cl2); 1H NMR (CD3OD,
400 MHz) d 3.55 (t, J=6.5 Hz, 2H), 2.28 (t, J=7.3 Hz,
2H), 1.59±1.54 (m, 2H), 1.45±1.41 (m, 4H); 13C NMR
(CD3OD, 100 MHz) d 161.5, 158.1, 87.2, 62.9, 33.6,
0.024 mmol) in CH2Cl2 (0.5 mL) was treated with tri-
¯uoroacetic acid (0.2 mL) at 25 ꢀC for 2 h. The solvent
was removed in vacuo to provide 47 (12.8 mg, 100%) as
a light yellow ®lm: 1H NMR (CF3COOD, 400 MHz)
d 5.75 (ddt, J=17.0, 10.4, 6.6 Hz, 1H), 5.05±5.00 (m,
2H), 2.39 (t, J=7.9 Hz, 2H), 2.12 (dt, J=6.9, 6.8 Hz,
2H), 1.59 (tt, J=7.7, 7.3 Hz, 2H); 13C NMR (CF3
COOD, 100 MHz) d 155.2, 151.4, 139.0, 117.8, 87.7,
34.1, 27.0, 22.6; IR (neat) nmax 3349, 3204, 2941, 1681,
28.6, 26.7, 24.0; IR (neat) nmax 3367, 3240, 2922, 2850,
1
1
1640, 1550, 1445, 1382, 1196, 1137, 1055 cm
;
1677, 1650, 1441, 1201, 1137, 842, 797 cm
;
FABHRMS (NBA) m/z 194.1408 (M++H, C9H15N5
requires 194.1406).
FABHRMS (NBA) m/z 212.1503 (M++H, C9H17N5O
requires 212.1511).
2,4,6-Tris[N,N-bis(t-butyloxycarbonyl)amino]-5-(5-hy-
droxypent-1-yl)pyrimidine (45). A solution of 44 (91 mg,
0.12 mmol) in anhydrous THF (0.3 mL) at 0 ꢀC was
2,4-Diamino-5-(5-hydroxypent-1-yl)-6-methylthiopyrimi-
dine (57). Following the procedure for the preparation
of 48, 55 provided 57 (87%) as a white ®lm: Rf 0.33
(SiO2, 10% CH3OH±CH2Cl2); 1H NMR (CD3OD,
400 MHz) d 3.55 (t, J=6.5 Hz, 2H), 2.42 (s, 3H), 2.42±
2.39 (m, 2H), 1.56 (tt, J=7.0, 7.0 Hz, 2H), 1.52±1.38 (m,
4H); 13C NMR (CD3OD, 100 MHz) d 167.4, 162.2,
161.7, 104.6, 63.0, 33.5, 28.5, 26.9, 26.6, 12.9; IR (neat)
nmax 3354, 3220, 2925, 2853, 1616, 1549, 1428, 1355,
1261, 1045 cm 1; FABHRMS (NBA) m/z 243.1288
(M++H, C10H18N4OS requires 243.1280).
.
treated with BH3 THF (1.0 M, 230 mL, 0.46 mmol) and
the reaction mixture was allowed to stir for 1 h. H2O
(25 mL) was added dropwise followed by aqueous 1.3 M
NaOH (177 mL) and aqueous 50% H2O2 (16 mL). The
mixture was stirred at 25 ꢀC for 1 h and extracted with
EtOAc (3Â5 mL). The organic layers were combined,
washed with H2O (2Â2 mL), and dried (MgSO4). Flash
chromatography (SiO2, 20±30% EtOAc±hexane) pro-
vided 45 (54 mg, 58%) as a white ®lm: Rf 0.30 (SiO2,
30% EtOAc±hexane); 1H NMR (CDCl3, 400 MHz) d
3.62 (t, J=5.4 Hz, 2H), 2.44 (t, J=6.4 Hz, 2H), 1.59±
1.55 (m, 4H), 1.42 (s, 54H); 13C NMR (CDCl3,
100 MHz) d 162.3, 156.1, 151.6, 150.5, 127.2, 84.4, 84.0,
62.2, 33.8, 27.8, 27.7, 27.5, 27.3, 26.7; IR (neat) nmax
3407, 2979, 2931, 1796, 1762, 1729, 1549, 1458, 1368,
1273, 1254, 1154, 1121, 850 cm 1; FABHRMS (NBA±
CsI) m/z 944.3670 (M++Cs, C39H65N5O13 requires
944.3633).
2,4,6-Tris[N,N-bis(t-butyloxycarbonyl)amino]-5-(5-oxo-
pent-1-yl)pyrimidine (46). A solution of 45 (18 mg,
22 mmol) in CH2Cl2 (250 mL) was treated with Dess±
Martin periodinane13 (o-Ph(CO2)I(OAc)3, 18 mg,
44 mmol) and the white suspension was stirred at 25 ꢀC
for 1 h. The mixture was diluted with Et2O (2 mL),
treated with aqueous 1.3 M NaOH (300 mL), and
extracted with Et2O (3Â2 mL). The organic layers were
combined, washed with H2O (1 mL), dried (MgSO4),
and concentrated. Flash chromatography (SiO2, 20%
EtOAc±hexane) provided 46 (16 mg, 89%) as a colorless
®lm: Rf 0.35 (SiO2, 30% EtOAc±hexane); 1H NMR
(CDCl3, 400 MHz) d 9.74 (t, J=1.6 Hz, 1H), 2.45 (t,
J=7.7 Hz, 2H), 2.41 (td, J=7.0, 1.6 Hz, 2H), 1.63±1.59
(m, 4H), 1.42 (s, 54H); 13C NMR (CDCl3, 100 MHz) d
201.6, 161.6, 156.0, 150.5, 150.0, 127.5, 84.1, 83.4, 43.5,
27.8, 27.7, 27.1, 26.3, 22.1; IR (neat) nmax 2980, 2920,
2,4-Bis[N,N-bis(t-butyloxycarbonyl)amino]-5-(5-hy-
droxypent-1-yl)-6-(methylthio)pyrimidine (55). Following
the procedure for the preparation of 45, 54 provided
55 (88%) as a colorless ®lm: Rf 0.30 (SiO2, 50%
EtOAc±hexane); 1H NMR (CDCl3, 400 MHz) d 3.64
(t, J=6.5 Hz, 2H), 2.55 (s, 3H), 2.55±2.49 (m, 2H),
1.60±1.52 (m, 6H), 1.44 (s, 18H), 1.40 (s, 18H); 13C
NMR (CDCl3, 100 MHz) d 172.7, 156.6, 155.2, 150.8,
150.0, 127.1, 83.7, 83.1, 62.7, 32.4, 27.9, 27.8, 27.2,
26.8, 25.9, 13.4; IR (neat) nmax 3486, 2978, 2928,
2868, 1792, 1757, 1732, 1553, 1528, 1458, 1393, 1364,
1274, 1254, 1154, 1115, 851, 776 cm 1; FABHRMS
(NBA) m/z 643.3344 (M++H, C30H50N4O9S requires
643.3377).
2850, 1793, 1763, 1723, 1554, 1365, 1275, 1256, 1151,
1
1116, 852, 778 cm
; FABHRMS (NBA±CsI) m/z
942.3448 (M++Cs, C39H63N5O13 requires 942.3477).
2,4-Bis[N,N-bis(t-butyloxycarbonyl)amino]-6-methylthio-
5-(5-oxopent-1-yl)pyrimidine (56). Following the proce-
dure for the preparation of 46, 55 provided 56 (91%) as

D. L. Boger et al./Bioorg. Med. Chem. 6 (1998) 643±659
a colorless ®lm: Rf 0.30 (SiO2, 20% EtOAc±hexane); 1H
659
References and Notes
NMR (CDCl3, 400 MHz) d 9.76 (t, J=1.6 Hz, 1H), 2.55
(s, 3H), 2.56±2.50 (m, 2H), 2.45 (td, J=7.1, 1.6 Hz, 2H),
1.74±1.66 (m, 2H), 1.64±1.58 (m, 2H), 1.44 (s, 18H), 1.40
(s, 18H); 13C NMR (CDCl3, 100 MHz) d 201.9, 172.7,
157.0, 155.3, 150.7, 150.0, 126.6, 83.7, 83.2, 43.5, 27.9,
27.8, 26.9, 26.3, 22.0, 13.4; IR (neat) nmax 2974, 2936,
1793, 1760, 1726, 1559, 1530, 1459, 1392, 1368, 1272,
1253, 1152, 1109, 851 cm 1; FABHRMS (NBA±CsI) m/
z 773.2210 (M++Cs, C30H48N4O9S requires 773.2196).
1. Boger, D. L.; Haynes, N.-E.; Kitos, P. A.; Warren, M. S.;
Ramcharan, J.; Marolewski, A. E.; Benkovic, S. J. Bioorg.
Med. Chem. 1997, 5, 1817. Boger, D. L.; Haynes, N.-E.; War-
ren, M. S.; Gooljarsingh, L. T.; Ramcharan, J.; Kitos, P. A.;
Benkovic, S. J. Bioorg. Med. Chem. 1997, 5, 1831. Boger, D. L.;
Haynes, N.-E.; Warren, M. S.; Ramcharan, J.; Kitos, P. A.;
Benkovic, S. J. Bioorg. Med. Chem. 1997, 5, 1839. Boger, D. L.;
Haynes, N.-E.; Warren, M. S.; Ramcharan, J.; Marolewski, A.
E.; Kitos, P. A.; Benkovic, S. J. Bioorg. Med. Chem. 1997, 5,
1847. Boger, D. L.; Haynes, N.-E.; Warren, M. S.; Ramcharan,
J.; Kitos, P. A.; Benkovic, S. J. Bioorg. Med. Chem. 1997, 5,
1853, and references cited therein.
5-(5-Oxopent-1-yl)-2,4,6-triaminopyrimidine tri¯uoro-
acetic acid salt (3). A solution of 46 (16 mg, 20 mmol) in
CH2Cl2 (0.5 mL) was treated with tri¯uoroacetic acid
(0.2 mL) at 25 ꢀC for 2 h. The solvent was removed in
vacuo to provide 3 (11.0 mg, 100%) as a light-yellow
®lm: 1H NMR (CF3COOD, 400 MHz) d 9.83 (br s, 1H),
2.69 (t, J=7.8 Hz, 2H), 2.43 (t, J=7.4 Hz, 2H), 1.83±
1.76 (m, 4H); 13C NMR (CF3COOD, 100 MHz) d 212.5,
2. Inglese, J.; Benkovic, S. J. Tetrahedron 1991, 47, 2351. Ing-
lese, J.; Blatchly, R. a.; Benkovic, S. J. J. Med. Chem. 1989, 32,
937.
3. For related studies, see: Li, S. W.; Nair, M. G. Med. Chem.
Res. 1991, 1, 353. Bigham, E. C.; Mallory, W. R.; Hodson, S.
J.; Duch, D. S.; Ferone, R.; Smith, G. K. Heterocycles 1993,
35, 1289.
155.3, 151.5, 87.2, 27.5, 25.6, 23.6, 22.7; IR (neat) nmax
4. Stura, E. A.; Johnson, D. L.; Inglese, J.; Smith, J. M.; Ben-
kovic, S. J.; Wilson, I. A. J. Biol. Chem. 1989, 264, 9703. Chen,
P.; Schulze-Gahmen, U.; Stura, E. A.; Inglese, J.; Johnson, D.
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J. Mol. Biol. 1995, 249, 153.
1
3367, 2920, 1683, 1445, 1206, 1140, 804, 805, 719 cm
;
FABHRMS (NBA) m/z 210.1350 (M++H, C9H15N5O
requires 210.1355).
2,4-Diamino-6-methylthio-5-(5-oxopent-1-yl)pyrimidine
tri¯uoroacetic acid salt (4). Following the procedure for
3, 56 provided 4 (100%) as a light-yellow ®lm: 1H NMR
(CF3COOD, 400 MHz) d 9.68 (br s, 1H), 2.74 (s, 3H),
2.73±2.62 (m, 2H), 2.64 (t, J=2.1 Hz, 2H), 1.79±1.75 (m,
2H), 1.58±1.50 (m, 2H); 13C NMR (CF3COOD,
100 MHz) d 212.6, 161.7, 156.5, 154.5, 107.6, 34.9, 27.4,
26.7, 22.7, 14.6; IR (neat) nmax 3426, 1679, 1443, 1206,
1138, 844, 800, 728 cm 1; FABHRMS (NBA) m/z
241.1130 (M++H, C10H16N4OS requires 241.1123).
5. Almassy, R. J.; Janson, C. A.; Kan, C.-C.; Hostomska, Z.
Proc. Natl. Acad. Sci. U.S.A. 1992, 89, 6114.
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Rosowsky, A.; Shih, C.; Moran, R. G. Biochemistry 1991, 30, 1997.
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istry; Wiley: New York, 1970; Vol. 7, pp 285±287. Rosowsky,
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GAR and AICAR Tfase inhibition studies
9. Loew, G. H.; Lawson, J. A.; Uyeno, E. T.; Toll, L.; Frenking,
G.; Polgar, W.; Ma, L. Y. Y.; Camerman, N.; Camerman, A.
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Characterization of the inhibitor properties was con-
ducted as previously described.1
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Cytotoxicity testing
11. Acharya, S. P.; Hynes, J. B. J. Heterocycl. Chem. 1975, 12,
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The cytotoxic activity of the agents was established fol-
lowing protocols described in detail.1
12. Taylor, E. C.; Otiv, S. R.; Durucasu, I. Heterocycles 1993,
36, 1883. Taylor, E. C.; Ray, P. S. J. Org. Chem. 1987, 52, 3997.
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Acknowledgements
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We gratefully acknowledge the ®nancial support of
the National Institutes of Health (CA663536 and
CA42056), The Skaggs Institute for Chemical Biology,
and the award of a NIH postdoctoral fellowship to
MJK (GM15429).
14. Boger, D. L.; Kochanny, M. J. J. Org. Chem. 1994, 59,
4950. Boger, D. L.; Dang, Q. J. Org. Chem. 1992, 57, 1631.
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