Chiral 6-aryl-furo[2,3-d]pyrimidin-4-amines as EGFR inhibitors

Article abstract of DOI:10.1016/j.ejmech.2016.04.054

Epidermal growth factor receptor inhibitors are of importance in cancer therapy and possibly in the management of pain. Herein, we report a structure-activity relationship study with 29 new 6-aryl-furo[2,3-d]pyrimidin-4-amines, involving modification of the 4-amino group and 6-aryl function. The EGFR activity was especially dependent on having a chiral 4-benzylamino group with correct stereochemistry. Molecular dynamics indicate this to be due to favourable cation-π interactions. The most active inhibitor identified, equipotent to Erlotinib, was substituted with (R)-1-phenylethylamine at C-4 and a N¹, N¹-dimethyl-1,2-diamine group in para position of the 6-aryl moiety. These new furopyrimidines had a different off-target kinase profile when compared to Erlotinib, and also possessed high activity towards Ba/F3 EGFR^L858R reporter cells. Further, comparing the EGFR data of the furo[2,3-d]pyrimidin-4-amines with that of the corresponding thieno- and pyrrolopyrimidines concludes the furopyrimidine scaffold to be highly useful for development of new epidermal growth factor receptor antagonists.

Full text of DOI:10.1016/j.ejmech.2016.04.054

Accepted Manuscript
Chiral 6-aryl-furo[2,3-d]pyrimidin-4-amines as EGFR inhibitors
Jin Han, Svein Jacob Kaspersen, Sondre Nervik, Kristin Nørsett, Eirik Sundby, Bård
Helge Hoff
PII:
S0223-5234(16)30347-6
10.1016/j.ejmech.2016.04.054
EJMECH 8569
DOI:
Reference:
To appear in: European Journal of Medicinal Chemistry
Received Date: 16 February 2016
Revised Date: 4 April 2016
Accepted Date: 22 April 2016
Please cite this article as: J. Han, S.J. Kaspersen, S. Nervik, K. Nørsett, E. Sundby, B.H. Hoff, Chiral 6-
aryl-furo[2,3-d]pyrimidin-4-amines as EGFR inhibitors, European Journal of Medicinal Chemistry (2016),
doi: 10.1016/j.ejmech.2016.04.054.
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Title Page
Manuscript: Chiral 6-aryl-furo[2,3-d]pyrimidin-4-amines as EGFR inhibitors
Jin Hana,b, Svein Jacob Kaspersena,c, Sondre Nervika, Kristin Nørsettd, Eirik Sundbyb, Bård
Helge Hoffa*
Adresses:
a)Norwegian University of Science and Technology, Department of Chemistry,
Høgskoleringen 5, NO-7491 Trondheim, Norway.b) Norwegian University of Science and
Technology, Institute of Chemistry and Material Technology, Faculty of Technology, NTNU,
7491 Trondheim. c) Current address: Jotun Marine and Protective Coatings, Rosenvoldsgt. 19,
NO-3202 Sandefjord, Norway.d)Norwegian University of Science and Technology,
Department of Cancer Research and Molecular Medicine, Prinsesse Kristinas gt. 1 N-7006
Trondheim, Norway.
Corresponding author:
* Bård H. Hoff, Department of Chemistry, Norwegian University of Science and Technology
(NTNU), NO-7491, Norway. Email: Bard.Helge.Hoff@chem.ntnu.no, phone:
++004773593973, fax: ++004773594256.
E-mail:
J. Han: Jin.Han@ntnu.no; S. J. Kaspersen: Svein.Jacob.Kaspersen@chem.ntnu.no; S. Nervik:
Sondre.Nervik@ntnu.no; K. Nørsett: Kristin.Norsett@ntnu.no; E. Sundby:
Eirik.Sundby@hist.no; B.H. Hoff: Bard.Helge.Hoff@chem.ntnu.no;
1

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Chiral 6-aryl-furo[2,3-d]pyrimidin-4-amines as EGFR inhibitors
Jin Hana,b, Svein Jacob Kaspersena,c, Sondre Nervika, Kristin Nørsettd, Eirik Sundbyb, Bård
Helge Hoffa*
a)Norwegian University of Science and Technology, Department of Chemistry, Høgskoleringen 5, NO-7491
Trondheim, Norway.b) Norwegian University of Science and Technology, Institute of Chemistry and Material
Technology, Faculty of Technology, NTNU, 7491 Trondheim. c) Current address: Jotun Marine and Protective
Coatings, Rosenvoldsgt. 19, NO-3202 Sandefjord, Norway.d)Norwegian University of Science and Technology,
Department of Cancer Research and Molecular Medicine, Prinsesse Kristinas gt. 1 N-7006 Trondheim, Norway.
Corresponding author: * Bård H. Hoff, Department of Chemistry, Norwegian University of Science and
Technology (NTNU), NO-7491, Norway. Email: Bard.Helge.Hoff@chem.ntnu.no, phone: ++004773593973,
fax: ++004773594256.
Abstract: Epidermal growth factor receptor inhibitors are of importance in cancer therapy and
possibly in the management of pain. Herein, we report a structure-activity relationship study
with 29 new 6-aryl-furo[2,3-d]pyrimidin-4-amines, involving modification of the 4-amino
group and 6-aryl function. The EGFR activity was especially dependent on having a chiral 4-
benzylamino group with correct stereochemistry. Molecular dynamics indicate this to be due
to favourable cation-π interactions. The most active inhibitor identified, equipotent to
Erlotinib, was substituted with (R)-1-phenylethylamine at C-4 and a N’,N’-dimethylethane-
1,2-diamine group in para position of the 6-aryl moiety. These new furopyrimidines had a
different off-target kinase profile when compared to Erlotinib, and also possessed high
activity towards Ba/F3 EGFRL858R reporter cells. Further, comparing the EGFR data of the
furo[2,3-d]pyrimidin-4-amines with that of the corresponding thieno- and pyrrolopyrimidines
concludes the furopyrimidine scaffold to be highly useful for development of new epidermal
growth factor receptor antagonists.
Keywords: Furopyrimidine; EGFR; Erlotinib; kinase, chiral drug
1 Introduction
Epidermal growth factor receptor (EGFR) signalling is important in the progression of
several tumour types [1-4], and there is evidence that this receptor also can be targeted in
pain treatment [5, 6]. Commercial small molecular EGFR inhibitors, examples including
Erlotinib, Gefitinib and Lapatinib, are based on the quinazoline scaffold [7, 8], while
investigational drugs containing thieno- [9, 10] and pyrrolopyrimidine [11-13] have also been
reported. Possibly, due to the bad reputation of furans as inducers of toxic effects [14], kinase
inhibitors based on furopyrimidines have been considerably less studied. However, some
examples exist including: I a receptor interacting protein 1 (RIP1) kinase inhibitor [15], II a
multikinase inhibitor [16], III an aurora kinase inhibitor [17], IV a dual vascular endothelial
growth factor 2 (VEGF2) and angiopoietin-1 receptor kinase (Tie-2) inhibitor [18]. In
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addition, Traxler found compound V to be a potent EGFR inhibitor [19], while Peng et al.
developed VI indicated selective for the EGFRL858R mutant [20]
, see Figure 1.
Figure 1. Examples of furopyrimidines previously evaluated as kinase inhibitors.
Herein we describe our structure-activity relationship (SAR) study and efforts towards potent
6-aryl-furo[2,3-d]pyrimidin-4-amines as EGFR inhibitors.
2 Result and Discussion
2.1 Design of the study
The main objective of the study was to identify new potent EGFR inhibitors based on the
furopyrimidine scaffold. This was inspired by our previous work on thieno- [9, 10, 21] and
pyrrolopyrimidines [13, 22, 23].
Figure 2. Structure of thieno-, pyrrolo- and the investigated furopyrimidines.
Compared to pyrrolopyrimidines, the furopyrimidines lack the N-H unit as presented by the
pyrrole, and in this way the furopyrimidine is a closer bioisoster of the thienopyrimidine, see
Figure 2. On the other hand, the size of the five-membered furan is more similar to the
pyrrole than the thiophene. As both these related scaffolds have been applied for construction
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of highly potent EGFR antagonists, we hypothesised that also the furopyrimidines should be
useful in this setting. Fourteen variations of the 6-aryl group (Fragment B) were investigated.
Eight derivatives were included for direct comparison with previous data in the thieno- and
pyrrolopyrimidine series (ortho-, meta- and para-methoxy, ortho-, meta- and para-phenolic,
para-fluorine and the unsubstituted analogue). Additionally, being structurally related to
tyrosine, the phenolic derivatives might engage in a number of interactions [24], while the
methoxy function is a moderately good hydrogen bond acceptor found useful in the
corresponding thieno- and pyrrolopyrimidine analogues [10, 13]. The para-bromo and para-
cyano compounds were mainly intended as precursor for other compounds. In the latter case,
this was not viable due to the low yield in synthesis. In the 4-amino group (Fragment A) we
included thirteen different variations. The selection was done both with the desire to yield
potent inhibitors and to study protein-ligand interaction. Nine of these sub-structural elements
have also been evaluated in the corresponding pyrrolopyrimidine series of compounds [13,
22].
2.2 Synthesis
The synthetic routes are outlined in Scheme 1 and 2. Starting with 1-aryl-2-bromoethanones
1, the 2-amino-5-aryl-3-cyanofurans 3, were made by a one-pot procedure using N’,N’-
diethylamine as base. Addition of reagents was done at 0 °C, followed by 4.5 - 6 hours
stirring at room temperature. The starting material was rapidly consumed and a build-up of
1
intermediate 2 was seen by H NMR spectroscopy. Work-up was done by quenching
followed by washing with water resulting in mediocre yield and purity. No defined by-
products were seen by 1H NMR spectroscopy, indicating impurities to be of polymeric origin.
Attempted further purification by silica-gel column chromatography or re-crystallisation
resulted in decomposition and loss of material. A change in colour was noticed when the
compounds were stored. Thus, we assume these furans to be unstable as indicated for similar
compounds [25].
Scheme 1. Synthetic route to the target compounds 6-18.
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The semi-pure furans 3 were then condensed with formamide in a formic acid/DMF mixture
at 150 °C. The product 4 could also be precipitated from water giving isolated yields in the
range of 38 to 63% from 3. Compounds 4 were then chlorinated using neat POCl3 leading to
the formation of the 6-aryl-furopyrimidines 5. Isolated yields were for most compounds in the
range of 75 - 89%. However, a low 16% yield was seen for the more labile cyano derivative.
A decrease in yield was also noticed when reactions were performed with stored materials of
4, indicating lability issues also with the furopyrimidones. Compounds 5a-g were all treated
with (R)-1-phenylethylamine to furnish the corresponding end-products 6a-g. Additionally,
derivative 5a was converted to 7a-18a using various primary amines. The reactions were in
most cases performed using n-butanol as solvent at reflux giving the products in 73 - 89%
yield.
Scheme 2. Post modifications on derivatives 6a, 6d, 6f and 6g.
The subsequent deprotection of the methyl ethers 6a, 6f and 6g using BBr3 gave the phenolic
analogues 6h, 6i and 6j in 76 - 82% isolated yield (Scheme 2). The bromo derivative 6d was
applied in both Suzuki and Buchwald type coupling to yield the vinyl analogue 6k and the
amine containing derivatives 6l-n, see Scheme 2. The purity of all end-products was analysed
by HPLC to be > 96% by area.
2.3 In vitro EGFR potency
2.3.1 Effect of modification of the 6-aryl group
The effect of the 6-aryl substitution pattern on the activity was investigated using (R)-1-
phenylethylamine as the 4-amino group. The choice of the amino group was based on our
previous SAR studies on the structurally related thieno- and pyrrolopyrimidines [10, 13]. The
activities in terms of IC50 values are summarised in Figure 3.
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Figure 3. Effect of variation of the 6-aryl group on the EGFR IC50 value (nM). (The
supplementary material file contain information on number of measurements and standard
deviations).
We initially evaluated the derivatives 6a-k in EGFR assays. The highest activity was seen for
compounds having electron donating substituents in ortho and para position, of which the
most potent derivatives were the phenols 6h and 6j. The binding interactions between EGFR
and derivatives 6b, 6g, 6h (see Supplementary Material) and 6j (see Figure 4) were
investigated by induced-fit docking with Schrödinger [26-28], and 10 ns molecular dynamics
using the Desmond suite, the OPL-3 force field and the TIP4P solvent model [29]. The
common binding motif seen for the four analogues includes a hydrogen bond between N-1
and Met793, a water mediated interaction between N-3 and Thr854, and what appears to be a
cation-π interaction between the aromatic part of the 4-amino group and Lys745. The ortho-
phenolic compound 6j is indicated to bind via two bridging water molecules to Cys797 and
Leu719, which may explain the high potency of this derivative. Dynamics also revealed
compound 6b to interact with Tyr998 via an unconventional hydrogen bond from the para-
position of the ligand to the Tyr998 centroid. This H-bond was not judged important for
compound 6g and 6j. The unsubstituted derivative 6b, and compounds with more lipophilic
substituents at the para position such as fluorine (6c), bromine (6d) or vinyl (6k) displayed
lower inhibitory potency. A mediocre activity was also noticed for the para-cyano containing
compound 6e.
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Figure 4. EGFR ligand interactions as identified by docking and molecular dynamics for 6j.
(The 2D representation of the 3-dimentional image wrongly shows the position of the ortho
substituent.) Docking and dynamics showed these to have an anti-relationship to the furan
oxygen.
Solubilising tails placed in para position of the 6-aryl group boosted potency for our related
thienopyrimidines [9]. As the initial structure-activity relationship data for the
furopyrimidines corresponded fairly well with that observed for the thieno-series, we
expected that structurally related furopyrimidines should be active. Molecular docking of 6l-
6n resulted in superior docking scores, which strengthened our assumption. Indeed, this
turned out to be the case, and the most potent derivative 6l, bearing a N’,N’-dimethylethane-
1,2-diamine group had an IC50 value of 0.4 nM, which is equipotent with the commercial
drug Erlotinib. The piperidine containing compound 6n was slightly less potent (IC50: 0.6
nM), while the morpholine analogue had an IC50 of 1.1 nM. The IC50 titration curves of
compounds 6b, 6j, 6l and 6n are compared in Figure 5.
Figure 5. IC50 curves with error bars of 6b (20 data points), 6j (20 data points), 6l (40 data
points) and 6n (40 data points).
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Binding interactions for 6l (Figure 6) and 6n (Supplementary Material) as analysed by
docking followed by 10 ns dynamics, revealed the pyrimidine core and Fragment A to be
positioned similar to that seen for 6b, 6g, 6h and 6j. Further, the higher activity of these
derivatives are indicated to be due to a hydrogen bonding network involving the N’,N’-
dimethylethane-1,2-diamine.
Figure 6. EGFR ligand interactions as identified by docking and molecular dynamics for 6l
(docking score: -12.47).
2.3.2 Effect of variation of the 4-amino group
Then the effect of varying the amine part (Fragment A) was investigated with 14 different
amines, using para-methoxyphenyl as the 6-aryl group (a-series), see Figure 7.
When installing alcohol groups in the R2-substituent (compound (S)-7a and (R)-12a), the
potency increased slightly compared with the benchmark (R)-configurated 6a. Note that the
change in absolute configuration is due to the Cahn-Ingold-Prelog priority rules, and not a
switch in stereopreference. The amide containing racemate 11a also demonstrated decent
activity. Lower potency was observed for the achiral derivative 8a and furopyrimidines
bearing fluorine substituents at the aromatic ring of Fragment A. To shed light on the
involvement of the aromatic ring in EGFR-ligand binding, compound 16a, in which the
phenyl was replaced by a cyclohexyl, and 17a, lacking the ring system, were prepared and
assayed. Both compounds possessed low inhibitory potency, revealing the crucial role of the
aromatic ring in binding with EGFR. This conclusion is in line with the interaction maps
shown in Figure 4 and 6 and what was observed in a study of thienopyrimidine based EGFR
inhibitors [30]. The (S)-configurated derivative 18a also had a low activity, which
corresponds with previous findings in the thienopyrimidine series [10, 21]. Clearly,
stereochemistry is of uttermost importance for EGFR inhibitory properties.
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Figure 7. Effect of varying the 4-amino group in the a-series on the EGFR IC50 values. (The
Supplementary Material file contain information on number of measurements and standard
deviations).
The major trend with respect to the effect of the 4-amino group on potency was similar also
in the b-series of compounds (4 examples, see Figure 7), which indicate very similar binding
mode. This further motivated us for combination of activity inducing groups into the same
molecule. Thus, we merged the functionality in compound 6h and 7b into the derivative 7h,
see Figure 8.
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Figure 8. Attempts to improve potency by combining activity inducing fragments.
Whereas compound 7h was fairly potent (IC50 of 2.0 nM), no improvement in activity was
seen as compared to derivative 6h. A possible reason could be that the desolvation cost for
this rather polar molecule is high as compared to the gain in protein-ligand binding energy.
2.3.3 Structure-activity relationship
The structure-activity relationship (SAR) information obtained, summarised in Figure 9,
shows that the major activity cliffs are when changing the amine part of Fragment A to
aliphatic amines or to amines having the opposite stereochemistry. Highest EGFR activity
was seen when R2 was hydroxymethyl, hydroxyethyl or methyl.
Figure 9. Structure activity relationship data obtained in this study.
Substitution of the 6-aryl group (Fragment B) allows for fine tuning of potency. Polar
substituents are preferred in terms of activity, and a boost in potency was seen for compounds
containing the NHCH2CH2NMe2 substituent in para position. Our previous studies on
thienopyrimidines [9, 10] did not contain data on compounds containing aliphatic amines in
Fragment A, or compounds containing NHCH2CH2NR2 groups in para position of Fragment
B. However, Figure 10 compares the IC50 values for those furopyrimidines in which the
corresponding thieno- or pyrrolopyrimidines also have been assayed for EGFR activity.
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Figure 10. Effect of scaffold hopping: EGFR activity of furo- vs. thieno- and
pyrrolopyrimidines. Numbering corresponds to the structure of the furopyrimidines. The
comparison contains data for 18 furopyrimidines, 18 pyrrolopyrimidines [13, 22] and 10
thienopyrimidines [9, 10].
The comparison reveals that the furopyrimidines on average results in more potent EGFR
inhibitors than the corresponding thienopyrimidines. The largest difference in activity
between the two scaffolds was for the para- and ortho-phenolic compounds 6h and 6j and
their thienopyrimidine counterparts. Molecular docking and dynamics were employed to aid
understanding of these differences. An overlay of the docked conformers of 6j and the
corresponding thienopyrimidine is shown in Figure 11.
Figure 11. Overlay of the docked structures 6j and the corresponding thienopyrimidine
analogue.
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As seen, the longer C-S bond lengths of the thienopyrimidines as opposed to the C-O bond in
furopyrimidines leads to a slight difference in the position of the 6-aryl group for the two
scaffolds. Thus, dynamics finds that the para-phenolic group engage in hydrogen bonding
with water molecules coordinated to different amino acid residues (see Supplementary
Material). Secondly, compound 6j appears to have the phenolic group in an anti, rather than
syn relationship relative to the furan oxygen. The thienopyrimidine analogue on the other
hand prefers a syn relationship, which might be explained by weak intramolecular O-S
interactions [31, 32]. Thus, computational chemistry predicts that the ortho-phenolic group of
6j interacts via two water molecules to Cys797 and Leu718 as shown in Figure 4. The ortho-
phenolic group in the thienopyrimidine analogue seems to be bonded via a water molecule to
Pro797 (Supplementary Material). The superior activity of the pyrrolopyrimidines is
explained by additional hydrogen bonding involving the pyrrolo N-H function. Overall, the
furopyrimidines appears as an attractive alternative to both quinazolines and
thienopyrimidines in development of EGFR inhibitors.
2.3.4 Kinase profiling and cell model
The two most potent furopyrimidines identified 6l and 6n, were profiled towards a panel of
50 additional kinases at 500 nM test concentration and compared with the profile of Erlotinib.
Gini plots and Gini coefficients [33] (see Supplementary Materials) revealed a similar
average selectivity profile. However, the fingerprint pattern was somewhat different. Figure
12 shows the main off-targets sorted by the activity displayed by compound 6n.
Figure 12. Kinase inhibition profile of 6l, 6n and Erlotinib sorted by the activity of 6n.
The main off-targets for the furopyrimidines includes CSF1R, FGR, YES, LYN B and ABL,
while low activity was seen towards HER2 and HER4. Inhibitors having dual activity
towards EGFR and CSF1R might be of value in treatment of glioblastoma [34]. Erlotinib in
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this panel had a higher inhibition than the furopyrimidines towards especially HER2 and
HER4, LYN A and B, KDR, Src and RET.
To reveal if the new furopyrimidines 6l and 6n also had on-target cellular potency, they were
compared with Erlotinib using Ba/F3-EGFRL858R reporter cells [35]. This system consists of a
murine bone marrow–derived cell line, which is dependent on interleukin-3 (IL-3), but is
rendered IL-3 independent by stable expression of the EGFRL858R oncogene. Cell
proliferation studies using the XTT assay proved both compounds to be active in the
nanomolar concentration range, with IC50 of 217 and 196 nM for 6l and 6n, respectively.
Erlotinib in this assay had an IC50 of 87 nM, see Figure 13.
Figure 13. Cell proliferation study of compounds 6l and 6n compared to Erlotinib using
Ba/F3-EGFRL858R cells. Each data point shown is the average of three independent replicates.
IC50: Erlotinib: 87±5; 6l: 217±24, 6n: 196±6.
3
Conclusion
Based on the furopyrimidine scaffold, a structure-activity investigation on EGFR has been
performed. The study showed that the activity was highly dependent on the substitution
pattern. In the 4-amino group, both the presence of a stereocentre with correct
stereochemistry and an unsubstituted phenyl ring boosts potency. Experimental and in silico
data indicate this to be partly due to favourable cation-π interactions. Preferable substituents
in the 6-aryl group includes solubilising tails containing amine functionality. The most potent
derivative was equipotent to the commercial drug Erlotinib, and profiling in a panel of 50
kinases revealed this compound to have other kinase off-targets, most importantly CSF1R.
Additionally, cellular studies using engineered Ba/F3 EGFRL858R cells showed two of the
furopyrimidines to have IC50 values in the nanomolar range. By comparing the EGFR activity
of furopyrimidines with that of the corresponding thieno- and pyrrolopyrimidines, the
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furopyrimidine was concluded to be an attractive scaffold for further development. Thus, new
active EGFR based inhibitors are likely to be found by further exploring the substitution
pattern of the meta- and para position of the 6-aryl group using polar substituents.
Experimental
4.1 General
1st generation BrettPhos, BrettPhos, NaBH4, boronic esters/acids, all the α-acetophenones and
nearly all amines were from Sigma Aldrich. (S)-2-Methoxy-1-phenylethanamine was
prepared and characterized in other studies from our laboratory [10]. (R)-3-Amino-3-
phenylpropan-1-ol was from Fluorochem. Silica-gel column chromatography was performed
using silica-gel 60A from Fluka, pore size 40-63 µm. Celite 545 from Fluka was also used.
4.2 Analyses
13
1H and C NMR spectra were recorded with Bruker Avance 400 spectrometer operating at
400 MHz and 100 MHz, respectively. 19F NMR was performed on a Bruker Avance 500
1
13
operating at 564 MHz. For H and C NMR chemical shifts are in ppm rel. to DMSO-d6,
while for 19F NMR the shift values are relative to hexafluorobenzene. Coupling constants are
in hertz. HPLC (Agilent 110-Series) with a G1379A degasser, G1311A Quatpump, G1313A
ALS autosampler and a G1315D Agilent detector (230 nm) was used to determine the purity
of the synthesised compounds. All compounds evaluated for EGFR inhibitory potency had a
purity of ≥96%. Conditions: Poroshell C18 (100×4.6 mm) column, flow rate 0.8 mL/min,
elution starting with water/CH3CN (90/10), 5 min isocratic elution, then linear gradient
elution for 35 min ending at CH3CN/water (100/0). The software used with the HPLC was
Agilent ChemStation. Accurate mass determination (ESI) was performed on an Agilent
G1969 TOF MS instrument equipped with a dual electrospray ion source. Accurate mass
determination in positive and negative mode was performed on a "Synapt G2-S" Q-TOF
instrument from Waters. Samples were ionized by the use of an ASAP probe, no
chromatography separation was used before the mass analysis. FTIR spectra were recorded
on a Thermo Nicolet Avatar 330 infrared spectrophotometer. All melting points are
uncorrected and measured by a Stuart automatic melting point SMP40 apparatus.
4.3 In vitro EGFR (ErbB1) inhibitory potency
The compounds were supplied in a 10 mM DMSO solution, and enzymatic EGFR (ErbB1)
inhibition potency was determined by Thermo Fisher Scientific (LifeTechnology) using their
Z’-LYTE® assay technology[36]. All compounds were first tested for their inhibitory activity
at 100 nM in duplicates. The potency observed at 100 nM was used to set starting point of
the IC50 titration curve, in which three levels were used 100, 1000 or 10000 nM. The IC50
values reported are based on the average of at least 2 titration curves (minimum 20 data
points), and were calculated from activity data with a four parameter logistic model using
SigmaPlot (Windows Version 12.0 from Systat Software, Inc.) Unless stated otherwise the
ATP concentration used was equal to Km. The average standard deviation for single point
measurements were <4%.
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4.4 In vitro kinase panel
The compounds were supplied in a 10 mM DMSO solution, and enzymatic kinase inhibition
potency was determined by Thermo Fisher Scientific (LifeTechnology) using their Z’-
LYTE® assay technology [1], at 500 nM in duplicates. ATP concentration used was equal to
Km, except when this service was not provided and other concentrations had to be used.
4.5 Ba/F3 reporter cell analysis
Transfected Ba/F3 cells containing expression vectors for the EGFRL858R mutant was a kind
gift from Dr. Nikolas von Bubnoff at the Technical University of Munich, Munich, Germany
[35]. The cells were cultured in RPMI 1640 (Gibco, Invitrogen) supplemented with 10% FCS
(Gibco, Invitrogen), 1% L-glutamine (Gibco, Invitrogen) and 0.1% Gentamycin (Sanofi
Aventis). Erlotinib was purchased from LC Laboratories (Woburn, MA). All inhibitors were
reconstituted in DMSO, and appropriate stock solutions were prepared using cell culture
medium. The final percentage concentrations of DMSO were < 0.2%. Proliferation analysis:
Ba/F3 cells (1 × 104 per well) were plated into 96-well plates. Inhibitors were added in
different concentrations as indicated. Cell growth was measured at 48 hours using TACS®
XTT Cell Proliferation Assay (Trevigen) according to the manufacturer’s instructions. Three
independent biological experiments were performed for each compound. All measurements
were performed in triplicate.
4.6.1 3-Amino-3-phenylpropanoic acid [37].
Malonic acid (9.81 g, 94.0 mmol) and ammonium formate (11.9 g, 188 mmol) were slurried
o
in EtOH (33 mL, 96%) at ambient temperature and heated to 60 C. Benzaldehyde (9.5 mL,
943.5 mmol) was added and temperature maintained below 65 oC. The reaction was reflux for
4 h and cooled to ambient temperature overnight. The reaction mixture was filtered, the
product washed with EtOH (10 mL) and dried in vacuo to yield 7.55 g of 3-amino-3-
phenylpropanoic acid as a white solid (45.1 mmol, 48%); mp: 223 - 224 oC (lit. 216 - 218 oC
[38], 224 oC [37]); 1H NMR (400 MHz, D2O): 7.52 - 7.45 (m, 5H), 4.67 (t, J = 6.9, 1H), 2.96
- 2.81 (m, 2H). 1H NMR spectroscopy match that previously reported [37].
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4.6.2 Methyl 3-amino-3-phenylpropanoate [37].
3-Amino-3-phenylpropanoic acid (2.00 g, 12.1 mmol) was slurried in MeOH (13 mL) and
o
cooled to -10 C. Concentrated H2SO4 (1.3 mL) was added over 45 min, maintaining the
o
temperature below 0 C. Once completion of the addition, the reaction was heated up to
ambient temperature and stirred for 5 h. The reaction mixture was reduced by half in vacuo
followed by addition of CH2Cl2 (2 x 14 mL). The pH of aqueous layer was adjusted with
NaOH (58 mL, 1M) to pH 12. The phases were separated and the organic phases were
washed with H2O (10 mL), dried over anhydrous Na2SO4 and concentrated in in vacuo to
1
obtain 2.02 g (11.1 mmol, 92%) of methyl 3-amino-3-phenylpropanoate as an clear oil; H
NMR (400 MHz, CDCl3-TMS): 7.36 - 7.24 (m, 5H), 4.42 (t, J = 6.9, 1H), 3.68 (s, 3H), 2.67 -
2.65 (m, 2H), 1.74 (s, br, 2H). 1H NMR spectroscopy match that previously reported [37].
4.6.3 3-Amino-3-propanamide [39].
Methyl 3-amino-3-phenylpropanoate (2.00 g, 11.2 mmol) was slurried in ammonia (25 mL,
25%) and stirred at ambient temperature overnight. The clear reaction mixture was
neutralised with aqueous NH4Cl (40 mL) and extracted with CH2Cl2 (2 x 40 mL). The
combined organic phases were dried over anhydrous Na2SO4 and concentrated in vacuo to
obtain 1.38 g (8.48, 76%) of 3-amino-3-propanamide as a white crystalline solid; mp 102 -
104 oC (lit. 99 – 101 oC [39], 110 oC [40]) 1H NMR (400 MHz, CDCl3-TMS): 7.38 - 7.25 (m,
5H), 6.89 (s, br, 1H), 5.60 (s, br, 1H), 4.35 (t, J = 6.9, 1H), 2.56 - 2.54 (m, 2H), 1.75 (s, br,
2H). 1H NMR spectroscopy match that previously reported [39, 40]
4.6.4 Synthesis of 2-(2-(4-methoxyphenyl)-2-oxoethyl)malononitrile (2a) [41].
2-Bromo-1-(4-methoxyphenyl)ethan-1-one (1a) (2.00 g, 8.73 mmol) was dissolved in ethanol
(50 mL) with malononitrile (606 mg, 9.17 mmol) and sodium ethoxide (653 mg, 9.60 mmol).
The reaction mixture was heated at 40 °C for 18 h before the solvent was removed under
reduced pressure. The crude product was triturated in cold methanol, filtrated and dried in
16

ACCEPTED MANUSCRIPT
vacuo. This yielded 1.25 g (5.85 mmol, 67%) of 2a as a white solid; mp: 148 - 154 °C; HPLC
1
purity: 99%, tR = 18.6 min; H NMR (400 MHz, CDCl3-TMS): δ: 7.93 (d, J = 8.9, 2H), 6.99
(d, J = 9.0, 2H), 4.41 (t, J = 6.9, 1H), 3.90 (s, 3H), 3.71 (d, J = 6.7, 3H); 13C NMR (100 MHz,
DMSO-d6): δ: 193.0, 164.4, 131.1, 128.3 (2C), 115.0 (2C), 114.6 (2C), 56.1, 38.3, 18.5; IR
(neat, cm-1): 2907, 1673, 1602, 1574, 1256, 1178, 1018, 834, 810, 574; HRMS (APCI/ASAP,
1
m/z): 215.0822 (calcd. C12H11N2O2, 215.0821, [M+H]+). H NMR spectroscopy match that
previously reported[42].
4.7 General procedure synthesis of 2-amino-5-arylfurane-3-carboxynitriles (3)
A solution of bromoketone (6 - 25 g) and malononitrile (1.3 eq.) was stirred at 0 °C in DMF
(6 mL/g) for 10 min. Diethylamine (2.2 eq) was added at 0 °C over 30 min using a syringe
pump and the mixture was stirred at 22 °C for 4.5 h. The solution was poured onto water and
left standing for 24 h at 0 ˚C. The formed precipitate was filtered off, washed with water (2 ×
50 mL) and petroleum ether (50 mL) and dried in vacuo to yield target compound.
4.7.1 2-Amino-5-(4-methoxyphenyl)furan-3-carbonitrile (3a) [42].
Compound 3a was prepared as described in Section 4.7 starting with 2-bromo-1-(4-
methoxyphenyl)ethan-1-one (20.0 g, 87.3 mmol) and malononitrile (7.50 g, 114 mmol). This
1
gave 7.00 g (32.7 mmol, 37%) as a brown solid, mp 178 °C (dec.); H NMR (400 MHz,
DMSO-d6) δ: 7.49 (s, 2 H), 7.42 (d, J = 8.8, 2 H), 6.95 (d, J = 8.8, 2H), 6.79 (s, 1 H), 3.76 (s,
3 H); 13C NMR (100 MHz, DMSO-d6) δ: 164.2, 158.6, 142.5, 124.2 (2C), 122.8, 116.7, 114.8
(2C), 104.9, 66.3, 55.6; IR (neat, cm-1): 3413, 3327, 2205, 1646, 1508, 1245, 1026, 828;
1
HRMS (EI): 214.0733 (calcd C12H10N2O2, 214.0737, [M]+). The previous H NMR reported
in DMSO-d6 differs with respect to the shift of the NH2 protons[42].
4.7.2 2-Amino-5-phenylfuran-3-carbonitrile (3b) [43].
Compound 3b was prepared as described in Section 4.7 starting with 2-bromo-1-phenylethan-
1-one (19.0 g, 95.6 mmol) and malononitrile (8.21 g, 124 mmol). This gave 8.61 g (46.7
1
mmol, 49%) of 3b as a brown solid; mp 193 °C (dec.) (lit. [44] 196-198°C); H NMR (400
MHz, DMSO-d6) δ: 7.61 (s, 2 H), 7.49 - 7.47 (m, 2 H),7.38 - 7.34 (m, 2H), 7.21 - 7.18 (m, 1
H), 6.98 (s, 1 H); 13C NMR (100 MHz, DMSO-d6) δ: 164.0, 141.8, 129.4, 128.8 (2C), 126.6,
122.1 (2C), 116.1, 106.7, 66.2; IR (neat, cm-1): 3412, 3323, 3112, 2206, 1645, 1610 1173,
754; HRMS (ESI): 185.0712 (calcd C11H9N2O, 185.0715, (M+H)+).
17

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4.7.3 2-Amino-5-(4-fluorophenyl)furan-3-carbonitrile (3c)
Compound 3c was prepared as described in Section 4.7 starting with 2-bromo-1-(4-
fluorophenyl)ethan-1-one (21.5 g, 97.0 mmol) and malononitrile (8.33 g, 126 mmol). This
gave 12.4 g (61.2 mmol, 63%) of 3c as a brown solid. mp 156 °C (dec.); 1H NMR (400 MHz,
13
DMSO-d6) δ: 7.60 (s, 2H), 7.52 - 7.49 (m, 2H), 7.23 - 7.19 (m, 2H), 6.95 (s, 1H); C NMR
(100 MHz, DMSO-d6) δ: 164.0, 162.3, 160.8 (d, J = 244.2), 141.1, 126.1 (d, J = 3.1), 124.1
(d, J = 8.1, 2C), 116.0, 115.9 (d, J = 22.0, 2C), 106.5; IR (neat, cm-1): 3408, 3322, 3252,
3197, 2205, 1643, 1571, 1500, 1232, 836; HRMS (APCI/ASAP, m/z): 203.0621 (calcd.
C11H8FN2O, 203.0621, [M+H]+).
4.7.4 2-Amino-5-(4-bromophenyl)furan-3-carbonitrile (3d) [45].
Compound 3d was prepared as described in Section 4.7 starting with 2-bromo-1-(4-
bromophenyl)ethan-1-one (15.0 g, 54.0 mmol) and malononitrile (4.64 g, 70.2 mmol). This
gave 3d in 6.55 g (24.9 mmol, 48%) as a brown solid; mp 182 °C (dec.); 1H NMR (400 MHz,
DMSO-d6) δ: 7.69 (s, 2H), 7.56 (d, J = 8.6, 2H), 7.42 (d, J = 8.6, 2H), 7.08 (s, 1H); 13C
NMR (100 MHz, DMSO-d6) δ: 164.6, 141.2, 132.2 (2C), 129.0, 124.4 (2C), 119.8, 116.4,
108.4, 66.9; IR (neat, cm-1): 3411, 3311, 2219, 1646, 1578, 824, 803; HRMS (EI): 261.9737
(calc for C11H7ON2Br, 261.9736, [M]+).
4.7.5 2-Amino-5-(4-cyanophenyl)furan-3-carbonitrile (3e) [42].
Compound 3d was prepared as described in Section 4.7 starting with 2-bromo-1-(4-
cyanophenyl)ethan-1-one (6.00 g, 26.8 mmol) and malononitrile (1.91 g, 28.9 mmol) using a
reaction time of 17 hours. This yielded 4.51 g (21.6 mmol, 75 %) of a yellow solid; mp. 245 -
1
254 °C (lit. 240 - 241 °C); H NMR (400 MHz, DMSO-d6) δ: 7.90 (s, 2H), 7.80 (app. d, J =
13
7.8, 2H), 7.60 (app. d, J = 8.4, 2H), 7.33 (s, 1H); C NMR (100 MHz, DMSO-d6) δ: 165.1,
140.4, 133.7, 133.3 (2C), 122.6 (2C), 119.5, 116.0, 111.9, 108.3, 67.8; IR (neat, cm-1): 3441,
3334, 2232, 2211, 1631, 1604, 1577, 1173, 830, 805; HRMS (EI): 210.0733 (calcd.
C12H8N2O2, 210.0736, [M]+). The 1NMR shift data corresponds with that previously reported
[42].
4.7.6 2-Amino-5-(3-methoxyphenyl)furan-3-carbonitrile (3f)
Compound 3f was prepared as described in Section 4.7 starting with 2-bromo-1-(3-
methoxyphenyl)ethan-1-one (25.0 g, 109 mmol) and malononitrile (9.37 g, 142 mmol). This
resulted in 13.7 g (64.0 mmol, 59%) as a brown solid, mp 180 °C (dec.); 1H NMR (400 MHz,
DMSO-d6) δ: 7.61 (s, 2H), 7.29 - 7.25 (m, 1H), 7.08 - 7.06 (m, 1H), 7.03 - 7.01 (m, 2H), 6.79
13
- 6.77 (m, 1H), 3.77 (s, 3H); C NMR (100 MHz, DMSO-d6)δ: 164.0, 159.6, 141.6, 130.6,
130.0, 116.1, 114.5, 112.3,107.3, 107.2, 66.2, 55.1; IR (neat, cm-1): 3392, 332, 3210, 2215,
152, 1570,1166, 1047, 768; HRMS (APCI/ASAP, m/z): 215.0817 (calcd. C12H11N2O2,
215.0821, [M+H]+).
4.7.7 2-Amino-5-(2-methoxyphenyl)furan-3-carbonitrile (3g)
Compound 3g was prepared as described in Section 4.7 starting with 2-bromo-1-(2-
methoxyphenyl)ethan-1-one (10.0 g, 43.7 mmol) and malononitrile (3.75 g, 56.8 mmol). This
gave 4.49 g (20.9 mmol, 48%) of 3g as a brown solid, mp 177 °C (dec.); 1H NMR (400 MHz,
18

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DMSO-d6) δ: 7.59 (s, 2H), 7.48 - 7.45 (m, 1H), 7.23 - 7.18 (m, 1H), 7.08 - 7.05 (m, 1H), 7.01
13
- 6.96 (m, 1H), 6.85 (s, 1H), 3.89 (s, 3H); C NMR (100 MHz, DMSO-d6) δ: 163.8, 154.8,
139.0, 128.1, 124.0, 121.1, 118.5, 116.7, 111.8, 111.3, 66.8, 56.1; IR (neat, cm-1): 3402,
3321, 2206, 1649, 1587, 1242, 1025, 748; HRMS (EI): 214.0740 (calcd. for C12H10O2N2,
214.0737, [M]+).
4.8 General procedure for preparing 6-aryl-furo[2,3-d]pyrimidin-4(3H)-one (4)
To a solution of 3a - 3g (0.50 - 13 g), formic acid (23 eq.), anhydrous DMF (30 eq.) and
excess of formamide (50 eq.) were added. The mixture was heated at 150 ˚C for 24 h before
cooling to 22 ˚C and then isopropanol (50-300 mL) was added. The mixture was left standing
for 72 h at 0 ˚C. The formed precipitate was isolated by filtration, washed with cold
isopropanol (0.5 - 50 mL) and n-hexane (2 × 2 - 15 mL), and drying in vacuo giving the
target compounds 4a - 4g.
4.8.1 6-(4-Methoxyphenyl)furo[2,3-d]pyrimidin-4(3H)-one (4a)
The reaction was performed as described in Section 4.8 giving 2.01 g (8.31 mmol, 30%) of
4a as a brown solid; mp > 300 °C; 1H NMR (400 MHz, DMSO-d6) δ: 12.61 (s, 1H), 8.11 (s,
13
1H), 7.79 (d, J = 8.7, 2H), 7.31 (s, 1H), 7.05 (d, J = 8.7, 2H), 3.82 (s, 3H); C NMR (100
MHz, DMSO-d6) δ: 164.6, 160.2, 158.7, 152.1, 146.6, 126.3 (2C), 122.1, 115.0 (2C), 110.0,
99.7, 55.8; IR (neat, cm-1): 3100, 2838, 1674, 1253, 817, 780, 625; HRMS (EI): 242.0691
(calcd C13H10N2O3, 242.070, [M]+).
4.8.2 Phenylfuro[2,3-d]pyrimidin-4(3H)-one (4b) [43].
The reaction was performed as described in Section 4.8 starting with 3b (10.2 g, 55.5 mmol).
1
This gave 4.47 g (21.1 mmol, 38%) of 4b as a brown solid; mp > 300 °C; H NMR (400
MHz, DMSO-d6) δ: 12.65 (s, 1H), 8.15 (s, 1H), 7.86 - 7.84 (m, 2H), 7.50 - 7.46 (m, 3H), 7.40
13
- 7.37 (m, 1H); C NMR (100 MHz, DMSO-d6) δ: 164.4, 158.2, 151.2, 146.7, 129.1 (2C),
128.9, 128.7, 124.1 (2C), 109.4, 101.2; IR (neat, cm-1): 3407, 3097, 2851, 1673, 1203, 928,
749; HRMS (APCI/ASAP, m/z): 213.0663 (calcd. C12H9N2O2, 213.0664, [M+H]+).
4.8.3 6-(4-Fluorophenyl)furo[2,3-d]pyrimidin-4(3H)-one (4c)
The reaction was performed as described in Section 4.8 starting with 3c (10.0 g, 49.5 mmol).
1
This gave 4c in 5.36 g (20.46 mmol, 41%) as a brown solid. mp >300 °C; H NMR (400
MHz, DMSO-d6) δ: 12.65 (s, 1H), 8.14 (s, 1H), 7.92 - 7.87 (m, 2H), 7.46 (s, 1H), 7.36 - 7.30
(m, 2H); 13C NMR (100 MHz, DMSO-d6) δ: 164.4, 162.2 (d, J = 246.6), 158.2, 150.4, 146.7,
19

ACCEPTED MANUSCRIPT
126.4 (d, J = 8.5, 2C), 125.6 (d, J = 3.3), 116.1 (d, J = 22.0, 2C), 109.4, 101.1; IR (neat, cm-
1): 3411, 3311, 2219, 1646, 1578, 824, 803; HRMS (EI): 261.9737 (calcd. for C12H7ON2F,
261.9736, [M]+).
4.8.4 6-(4-Bromophenyl)furo[2,3-d]pyrimidin-4(3H)-one (4d)
The reaction was performed as described in Section 4.8 starting with 3d (526 mg, 2.00
1
mmol). This gave 360 mg (1.23 mmol, 61%) of 4d as brown solid; mp > 300 °C; H NMR
(400 MHz, DMSO-d6) δ: 12.68 (s, 1H), 8.17 (s, 1H), 7.81 (d, J = 8.6, 2H), 7.68 (d, J = 8.6,
2H), 7.56 (s, 1H); 13C NMR (100 MHz, DMSO-d6) δ: 165.0, 158.7, 150.6, 147.4, 132.5 (2C),
128.7, 126.6 (2C), 122.3, 109.9, 102.6; IR (neat, cm-1): 3413, 3095, 2852, 1676, 928, 815,
779; HRMS (EI): 289.9687 (calcd. for C12H7O2N2Br, 289.9685, [M]+)
4.8.5 6-(4-Cyanophenyl)furo[2,3-d]pyrimidin-4(3H)-one (4e)
The reaction was performed as described in Section 4.8 starting with 3e (2.00 g, 9.56 mmol).
This gave 1.63 g (6.87 mmol, 72%) of a red highly impure solid. NMR spectroscopy was
inconclusive on the identity of the components, however HRMS (EI): 238.0613 (calcd.
C13H10N2O3, 238.0617, [M] +) indicated the presence of the target product 4e.
4.8.6 6-(3-Methoxyphenyl)furo[2,3-d]pyrimidin-4(3H)-one (4f)
The reaction was performed as described in Section 4.8 starting with 3f (13.1 g, 61.2 mmol).
This gave 4.63 g (21.6 mmol, 35%) of 4f as a brown solid, mp >300 °C; 1H NMR (400 MHz,
DMSO-d6) δ: 12.64 (s, 1H), 8.14 (s, 1H), 7.52 (s, 1H), 7.44 - 7.37 (m, 3H), 6.97 - 6.94 (m,
1H), 3.83 (s, 3H); 13C NMR (100 MHz, DMSO-d6) δ: 164.4, 159.7, 158.2, 151.1, 146.7,
130.2 (2C), 116.5, 114.7, 109.4, 109.2, 101.6, 55.3; IR (neat, cm-1): 3392, 3320, 3210, 2215,
1520, 1570, 1166, 1047, 768; HRMS (APCI/ASAP, m/z): 243.0768 (calcd. C13H11N2O3,
243.0770, [M+H]+).
4.8.7 6-(2-Methoxyphenyl)furo[2,3-d]pyrimidin-4(3H)-one (4g)
The reaction was performed as described in Section 4.8 starting with 3g (3.00 g, 14.0 mmol).
1
This gave 1.41 g (5.82 mmol, 42%) of 4g as a brown solid; mp > 300 °C; H NMR (400
MHz, DMSO-d6)δ: 12.63 (s, 1H), 8.15 (s, 1H), 7.84-7.81 (m, 1H), 7.42 - 7.37 (m, 1H), 7.28
13
(s, 1H), 7.21 - 7.18 (m, 1H), 7.12-7.08 (m, 1H), 3.98 (s, 3H); C NMR (100 MHz, DMSO-
d6)δ: 164.2, 158.7, 156.4, 148.4, 147.1, 130.3, 126.2, 121.3, 117.7, 112.3, 109.8, 105.3, 56.1;
IR (neat, cm-1): 3402, 3321, 2206, 1649, 1587, 1242, 1025, 748; HRMS (EI): 242.0688 (calcd
C13H10N2O3, 242.0686, [M]+).
20

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4.9 General procedure synthesis of 6-aryl 4-chloro-furo[2,3-d]pyrimidines (5)
Compounds 4a - 4g (0.50 – 4.25 g) and neat POCl3 (0.15 g/mL) were mixed and reacted at 90
◦C for 3 - 10 h. The solution was poured onto ice and water (5 - 60 mL) was added. NaOH (8
M, 6 - 80 mL) was used to adjust the pH to 12. The precipitated material was isolated by
filtration and washed with water (20 - 200 mL) and n-pentane (20 - 200 mL). Drying under
reduced pressure gave wanted crude products. Purification on silica-gel was performed as
described for each individual compound 5a - 5g.
4.9.1 4-Chloro-6-(4-methoxyphenyl)furo[2,3-d]pyrimidine (5a) [17].
The reaction was performed as described in Section 4.9 starting with compound 4a (1.71 g,
7.05 mmol). Silica-gel column chromatography (EtOAc, Rf = 0.69) gave 1.65 g (6.34 mmol,
1
90%) of 5a as a yellow solid: mp 173 - 174 °C; H NMR (400 MHz, DMSO-d6) δ: 8.78 (s,
1H), 8.01 - 7.98 (m, 2H), 7.59 (s, 1H), 7.15 - 7.12 (m, 2H), 3.86 (s, 3H); 13C NMR (100
MHz, DMSO-d6) δ: 166.6, 162.6, 156.9, 152.7, 151.2, 127.8 (2C), 120.7, 120.1, 115.3 (2C),
97.0, 55.9; IR (neat, cm-1): 2978, 2842, 1502, 1245, 835, 768; HRMS (EI): 260.0348 (calcd
C13H9N2O2Cl, 260.0347 [M]+). 1H NMR shifts corresponds with that reported [46].
4.9.2 4-Chloro-6-phenylfuro[2,3-d]pyrimidine (5b) [43].
The reaction was performed as described in Section 4.9 starting with compound 4b (500 mg,
2.36 mmol). Purification by silica-gel column chromatography (EtOAc, Rf = 0.78) gave 412
1
mg (1.79 mmol, 76%) of 5b as a yellow solid; mp 152 - 154 °C; H NMR (400 MHz,
13
DMSO-d6) δ: 8.82 (s, 1H), 8.05 - 8.02 (m, 2H), 7.75 (s. 1H), 7.59 - 7.51 (m, 3H); C NMR
(100 MHz, DMSO-d6) δ: 166.2, 156.1, 152.7, 151.4, 130.5, 129.3 (2C), 127.8, 125.5 (2C),
119.3, 98.6; IR (neat, cm-1): 3105, 1557, 1252, 756; HRMS (APCI/ASAP, m/z): 231.0329
(calcd. C12H8N2OCl, 231.0325, [M+H]+).
4.9.3 4-Chloro-6-(4-fluorophenyl)furo[2,3-d]pyrimidine (5c)
The reaction was performed as described in Section 4.9 starting with compound 4c (1.66 g,
7.21 mmol). Purification by silica-gel column chromatography (EtOAC, Rf = 0.73) gave 1.59
1
g (6.39 mmol, 89%) of 5c as a yellow solid; mp 172 - 175 °C; H NMR (400 MHz, DMSO-
13
d6) δ: 8.82 (s, 1H), 8.12 - 8.07 (m, 2H), 7.73 (s, 1H), 7.45 - 7.39 (m, 2H); C NMR (100
MHz, DMSO-d6) δ: 166.6, 163.7 (d, J = 249.0), 155.7, 153.2, 151.9, 128.5 (d, J = 8.77, 2C),
124.3 (d, J = 3.4), 119.8, 116.9 (d, J = 22.4, 2C), 99.1; IR (neat, cm-1): 3075, 1502, 1239,
836, 769; HRMS (EI): 248.0150 (calcd. C12H6N2OClF, 248.0147, [M]+).
21

ACCEPTED MANUSCRIPT
4.9.4 6-(4-Bromophenyl)-4-chlorofuro[2,3-d]pyrimidine (5d)
The reaction was performed as described in Section 4.9 starting with compound 5d (4.25 g,
14.5 mmol). Purification by silica-gel column chromatography (n-pentane/EtOAc, 1/1, Rf =
0.86) gave 3.99 g (12.9 mmol, 88%) as a yellow solid; mp 193 - 194 °C; 1H NMR (400 MHz,
13
DMSO-d6) δ: 8.85 (s, 1H), 8.02 - 7.98 (m, 2H), 7.84 (s, 1H), 7.81 - 7.77 (m, 2H); C NMR
(100 MHz, DMSO-d6) δ: 166.7, 155.5, 153.5, 152.1, 132.8 (2C), 127.9 (2C), 127.5, 124.4,
119.8, 99.9; IR (neat, cm-1): 3111, 1561, 968, 809, 779; HRMS (EI): 307.9352 (calcd. for
C12H6ON2BrCl, 307.9347, [M]+).
4.9.5 4-(4-Chlorofuro[2,3-d]pyrimidin-6-yl)benzonitrile (5e)
Compound 5e was prepared using the procedure in Section 4.9 using crude material described
in Section 3.5.5 (1.50 g). Purification by silica-gel column chromatography (EtOAc, Rf =
0.74) gave 273 mg (1.07 mmol, 17%) of 5e as a red solid; mp. 170 - 171 °C; HPLC purity:
1
83%, tR = 21.9 min; H NMR (400 MHz, DMSO-d6) δ: 8.88 (s, 1H), 8.21 (d, J = 8.2, 2H),
13
8.03 (d, J = 8.2, 2H), 8.00 (s, 1H); C NMR (100 MHz, DMSO-d6) δ: 166.8, 154.5, 154.1,
152.8, 132.7 (2C), 132.4, 126.6 (2C), 119.6, 118.8, 112.9, 102.3; IR (neat, cm-1): 3105, 2922,
2850, 2231, 1563, 1376, 1253, 979, 844, 777; HRMS (APCI/ASAP, m/z): 260.0435 (calcd.
C13H7ClN2O, 260.0431, [M+H]+).
4.9.6 4-Chloro-6-(3-methoxyphenyl)furo[2,3-d]pyrimidine (5f) [17].
Compound 5f was prepared using the procedure in Section 4.9 using compound 4f (4.00 g,
16.5 mmol). Purification by silica-gel column chromatography (EtOAc, Rf =0.78) gave 3.76 g
(14.4 mmol, 87%) of 5f as a yellow solid; mp 157 - 160 °C; 1H NMR (400 MHz, DMSO-d6)
δ: 8.82 (s, 1H), 7.81 (s, 1H), 7.63 - 7.59 (m, 2H), 7.50 - 7.46 (m, 1H), 7.11 - 7.08 (m, 1H),
3.87 (s, 3H); 13C NMR (100 MHz, DMSO-d6) δ: 166.2, 159.8, 155.9, 152.8, 151.5, 130.5,
129.1, 119.3, 117.8, 116.8, 110.4, 99.0, 55.5; IR (neat, cm-1): 3103, 1560, 774; HRMS
(APCI/ASAP, m/z): 261.0429 (calcd. C13H10N2O2Cl, 261.0431, [M+H]+).
4.9.7 4-Chloro-6-(2-methoxyphenyl)furo[2,3-d]pyrimidine (5g) [17].
Compound 5g was prepared using the procedure in Section 4.9 using compound 4g (1.15 g,
4.76 mmol). Purification by silica-gel column chromatography (EtOAc/n-pentane 4/1, Rf =
0.60) gave 1.02 g (3.91 mmol, 83%) of 5f as a yellow solid; mp 156 - 157 °C ; 1H NMR (400
MHz, DMSO-d6) δ: 8.83 (s, 1H), 8.00 - 7.97 (m, 1H), 7.56 - 7.51 (m, 1H), 7.43 (s, 1H), 7.30 -
7.27 (m, 1H), 7.19-7.15 (m, 1H), 4.04 (s, 3H); 13C NMR (100 MHz, DMSO-d6) δ: 165.9,
157.6, 153.2 (2C), 152.8, 132.4, 127.6, 121.4, 119.8, 116.4, 112.6, 102.3, 56.4; IR (neat, cm-
1): 3075, 1245, 746; HRMS (EI): 260.0349 (calcd. C13H9N2O2Cl, 260.0347, [M]+).
22

ACCEPTED MANUSCRIPT
4.10 Amination of 6-aryl-4-chlorofuro[2,3-d]pyrimidines
Compounds 5a - 5g (0.125 - 1.84 g) and (R)-1-phenylethan-1-amine (3.0 eq.) were added to a
dry bottle containing n-butanol (1 mL/100 mg) and heated at 145 ˚C for several hours. After
cooling down to 22 ˚C, diethyl ether or EtOAc (10 - 150 mL) was added and the mixture was
washed with water (15 - 80 mL) and saturated aq. NaCl solution (10 - 60 mL), dried over
Na2SO4 and concentrated in vacuo. Purification on silica-gel as described for the respective
compounds 6a - 6g.
4.10.1 (R)-6-(4-Methoxyphenyl)-N-(1-phenylethyl)furo[2,3-d]pyrimidin-4-amine (6a)
The synthesis was performed as described in Section 4.10 starting with 5a (350 mg, 1.34
mmol) and (R)-1-phenylethan-1-amine (487 mg, 0.52 mL, 4.02 mmol, 3.0 eq.). Silica-gel
column chromatography (n-pentane/EtOAc 1/1, Rf = 0.63) gave 412 mg (1.19 mmol, 89%) of
6a as a white solid; mp 131 - 133 ˚C; HPLC purity: 99%, tR = 30.3 min; [ꢀ]ꢂꢁꢃ = -251.2 (c
1
1.01, DMSO); H NMR (400 MHz, DMSO-d6): δ: 8.26 - 8.24 (m, 1H), 8.17 (s, 1H), 7.74 -
7.70 (m, 2H), 7.44 - 7.41 (m, 2H), 7.34 - 7.30 (m, 3H), 7.24 - 7.20 (m, 1H), 7.10 - 7.07 (m,
13
2H), 5.49 - 5.42 (m, 1H), 3.82 (s, 3H), 1.55 (d, J = 7.1, 3H); C NMR (100 MHz, DMSO-
d6): δ: 166.1, 160.2, 156.6, 153.7, 151.1, 145.3, 128.8 (2C), 127.1, 126.5 (2C), 126.2 (2C),
122.3, 115.2 (2C), 103.3, 97.3, 55.8, 49.5, 23.2; IR (neat, cm-1): 3422, 2965, 1594, 1250,
1140, 1023, 778, 701; HRMS (APCI/ASAP, m/z): 346.1549 (calcd. C21H20N3O2, 346.1556,
[M+H]+).
4.10.2 (R)-6-Phenyl-N-(1-phenylethyl)furo[2,3-d]pyrimidin-4-amine (6b)
The synthesis was performed as described in Section 4.10 starting with 5b (150 mg, 0.65
mmol). Silica-gel column chromatography (EtOAc/n-pentane 8/2, Rf = 0.39) gave 152 mg,
(0.483 mmol, 74%) of 6b as a white solid, mp 128 - 131 ˚C; HPLC purity: 98%, tR = 30.4
min; [ꢀ]ꢂꢁꢃ = -252.1 (c 0.85, DMSO); 1H NMR (400 MHz, DMSO-d6) δ: 8.35 - 8.33 (m, 1H),
8.21 (s, 1H), 7.81 - 7.78 (m, 2H), 7.54 - 7.50 (m, 3H), 7.44 - 7.39 (m, 3H), 7.35 - 7.31 (m,
13
2H), 7.24 - 7.20 (m, 1H), 5.51 - 5.44 (m, 1H), 1.55 (d, J = 7.0, 3H); C NMR (100 MHz,
23

ACCEPTED MANUSCRIPT
DMSO-d6): δ: 165.8, 156.2, 153.7, 150.2, 144.7, 129.2 (2C), 128.8, 128.3 (2C), 126.7, 126.0
(2C), 124.1 (2C), 120.2, 102.5, 99.2, 49.3, 22.7; IR (neat, cm-1): 3269, 3029, 2973, 1597, 755,
688; HRMS (APCI/ASAP, m/z): 316.1449 (calcd. C20H18N3O, 316.1450, [M+H]+).
4.10.3 (R)-6-(4-Fluorophenyl)-N-(1-phenylethyl)furo[2,3-d]pyrimidin-4-amine (6c)
The synthesis was performed as described in Section 4.10 starting with 5c (150 mg, 0.603
mmol). Silica-gel column chromatography (EtOAc/n-pentane 1/1, Rf = 0.24) gave 148 mg
(0.44 mmol, 73%) of 6c as a white solid; mp 121 - 124 ˚C; HPLC purity: 98%, tR = 30.9 min;
[ꢀ]ꢂꢁꢃ = -228.7 (c 1.14, DMSO); 1H NMR (400 MHz, DMSO-d6) δ: 8.35 - 8.33 (m, 1H), 8.20
(s, 1H), 7.85 - 7.81 (m, 2H), 7.46 - 7.42 (m, 3H), 7.38 - 7.31 (m 4H), 7.24 - 7.20 (m, 1H),
13
5.49 - 5.43 (m, 1H), 1.55 (d, J = 7.0, 3H); C NMR (100 MHz, DMSO-d6) δ: 165.8, 162.2
(d, J = 246.6), 156.2, 153.7, 149.4, 144.7, 128.3 (2C), 126.7, 126.4 (d, J = 8.2, 2C), 126.0
(2C), 125.9, 116.3 (d, J = 22.1, 2C), 102.5, 99.0, 49.3, 22.6; IR (neat, cm-1): 3269, 2973,
1593, 1499, 698; HRMS (APCI/ASAP, m/z): 334.1356 (calcd. C20H17N3OF, 334.1356,
[M+H]+).
4.10.4 (R)-6-(4-Bromophenyl)-N-(1-phenylethyl)furo[2,3-d]pyrimidin-4-amine (6d)
The synthesis was performed as described in Section 4.10 starting with 5d (1.84 g, 5.95
mmol). Silica-gel column chromatography (CH2Cl2/MeOH 99/1, Rf = 0.38) followed by a re-
slurry in Et2O (15 mL) gave 1.85 g (4.71 mmol, 79%) of 6d as a white solid, mp 157 - 158
1
˚C; HPLC purity: 99%, tR = 33.4 min; [ꢀ]ꢂꢁꢃ= -244.3 (1.00, DMSO); H NMR (400 MHz,
DMSO-d6) δ: 8.39 - 8.37 (m, 1H), 8.21 (s, 1H), 7.74 - 7.69 (m, 4H), 7.54 (s, 1H), 7.44 - 7.42
(m, 2H), 7.34 - 7.31 (m, 2H), 7.24 - 7.20 (m, 1H), 5.50 - 5.43 (m, 1H), 1.55 (d, J = 7.0, 3H);
13C NMR (100 MHz, DMSO-d6) δ: 165.9, 156.2, 154.0, 149.1, 144.6, 132.2 (2C), 128.3 (2C),
126.7, 126.0 (5C), 121.7, 102.5, 100.0, 49.3, 22.6; IR (neat, cm-1): 3412, 2969, 1595, 1479,
773; HRMS (APCI/ASAP, m/z): 394.0550 (calcd. C20H17N3OBr, 394.0555, [M+H]+).
24

ACCEPTED MANUSCRIPT
4.10.5 (R)-4-(4-((1-phenylethyl)amino)furo[2,3-d]pyrimidin-6-yl)benzonitrile (6e)
Compound 6e was prepared as described in section 4.10 starting with 5e (125 mg, 0.49
mmol). Silica-gel column chromatography (EtOAc/n-pentane, 1/1, Rf = 0.51) yielded 404 mg
(1.12 mmol, 73%) of a white solid; mp 163 - 176 °C; HPLC purity: 99%, tR = 23.9 min;
[ꢀ]ꢂꢁꢃ= -205.2 (c 0.96, DMSO); 1H NMR (400 MHz, DMSO-d6) δ: 8.49 (d, J = 7.8, 1H), 8.24
(s, 1H), 7.94 - 7.90 (m, 4H), 7.70 (s, 1H), 7.42 (d, J = 7.2, 2H), 7.33 (t, J = 7.8, 2H), 7.22 (t, J
13
= 7.3, 1H), 5.51 - 5.44 (m, 1H), 1.55 (d, J = 7.0, 3H); C NMR (100 MHz, DMSO-d6) δ:
166.2, 156.4, 154.6, 148.2, 144.5, 133.2, 133.1 (2C), 129.9, 128.3 (2C), 126.7 (2C), 126.0,
124.5 (2C), 118.6, 110.5, 102.6, 49.3, 22.5; IR (neat, cm-1): 3360, 3056, 3028, 2977, 2927,
2227, 1594, 1493, 1309, 1138, 925, 945, 779, 696; HRMS (APCI/ASAP, m/z): 341.1400
(calcd. C21H17N4O, 341.1402, [M+H]+).
4.10.6 (R)-6-(3-Methoxyphenyl)-N-(1-phenylethyl)furo[2,3-d]pyrimidin-4-amine (6f)
Compound 6f was prepared as described in section 4.10 starting with 5f (300 mg, 1.15
mmol). Silica-gel column chromatography (n-pentane/EtOAc, 3/2, Rf = 0.36) gave 323 mg
(0.94 mmol, 81%) of 6f as a white solid; mp 131 - 133 °C; HPLC purity: 98%, tR = 30.7 min;
[ꢀ]ꢂꢁꢃ = -267.4 (c 1.04, DMSO); 1H NMR (400 MHz, DMSO-d6) δ: 8.35 - 8.33 (m, 1H), 8.21
(s, 1H), 7.51 (s, 1H), 7.44 - 7.41 (m, 3H), 7.38 - 7.28 (m, 4H), 7.24 - 7.20 (m, 1H), 6.99 -
13
6.97 (m, 1H), 5.50 - 5.43 (m, 1H), 3.85 (s, 3H), 1.55 (d, J = 7.0, 3H); C NMR (100 MHz,
DMSO-d6) δ: 165.8, 159.7, 156.2, 153.8, 150.1, 144.7, 130.49, 130.44, 128.3 (2C), 126.7,
126.0 (2C), 116.5, 114.8, 108.9, 102.5, 99.6, 55.2, 49.3, 22.7; IR (neat, cm-1): 3422, 2965,
1594, 1250, 1140, 1023, 778, 701; HRMS (APCI/ASAP, m/z): 346.1552 (calcd. C21H20N3O2,
346.1556, [M+H]+).
25

ACCEPTED MANUSCRIPT
4.10.7 (R)-6-(2-Methoxyphenyl)-N-(1-phenylethyl)furo[2,3-d]pyrimidin-4-amine (6g)
Compound 6g was prepared as described in section 4.10 starting with 5g (338 mg, 1.31
mmol. Silica-gel column chromatography (EtOAc, Rf = 0.60) gave 381 mg (1.10 mmol, 85%)
of 6g as a white solid; mp 107 - 110 °C ; HPLC purity: 99%, tR = 30.8 min; [ꢀ]ꢂꢁꢃ = -296.6 (c
1.00, DMSO-d6); 1H NMR (400 MHz, DMSO-d6) δ: 8.36 - 8.34 (m, 1H), 8.20 (s, 1H), 7.87-
7.84 (m, 1H), 7.67 (s, 1H), 7.45 - 7.42 (m, 2H), 7.41 - 7.37 (m, 1H), 7.35 - 7.31 (m, 2H),
7.25-7.20 (m, 2H), 7.12 - 7.08 (m, 1H), 5.53 - 5.46 (m, 1H), 4.02 (s, 3H), 1.56 (d, J = 7.0,
3H); 13C NMR (100 MHz, DMSO-d6) δ: 165.4, 156.5 (2C), 154.1, 147.3, 145.3, 130.1, 128.8
(2C), 127.1, 126.5 (2C), 126.3, 121.3, 118.2, 113.5, 112.3, 104.1, 56.2, 49.6, 23.1; IR (neat,
cm-1): 3258, 2971, 1593, 749, 698; HRMS (APCI/ASAP, m/z): 346.1551 (calcd. C21H20N3O2,
346.1556, [M+H]+).
4.11 Post modifications
4.11.1 (R)-4-(4-((1-Phenylethyl)amino)furo[2,3-d]pyrimidin-6-yl)phenol (6h)
(R)-4-(4-((1-Phenylethyl)amino)furo[2,3-d]pyrimidin-6-yl)phenol (6a) was dissolved in dry
CH2Cl2 (2 mL) under nitrogen atmosphere. BBr3 (0.17 mL, 1.8 mmol) in dry CH2Cl2 (1.5
mL) was added drop wise at 0 ˚C over 1 h using a syringe pump. Then the mixture was
allowed to react at rt for 24 h. The reaction was quenched by addition of water (10 mL), and
the mixture was extracted with EtOAc (3 × 25 mL). The combined organic phase was washed
with brine (15 mL), dried over Na2SO4 and concentrated in vacuo. The crude product was
purified by silica-gel column chromatography (EtOAc/n-pentane, 8/2, Rf = 0.49). The product
was further crystallised from diethyl ether (2 mL) by slowly adding n-pentane (30 mL).
Evaporation and concentration in vacuo gave 114 mg (0.343 mmol, 80%) of 6g as a white
solid; mp 134 -136 °C; HPLC purity: 96%, tR = 26.3 min; [ꢀ]ꢂꢁꢃ = -269.4 (c 0.59, DMSO);
1H NMR (400 MHz, DMSO-d6) δ: 9.88 (s, 1H), 8.23 - 8.21 (m, 1H), 8.16 (s, 1H), 7.62 - 7.60
(m, 2H), 7.43 - 7.41 (m, 2H), 7.33 - 7.31 (m, 2H), 7.25 - 7.19 (m, 2H), 6.91 - 6.89 (m, 2H),
26

ACCEPTED MANUSCRIPT
13
5.49 - 5.42 (m, 1H), 1.54 (d, J = 7.0, 3H); C NMR (100 MHz, DMSO-d6) δ: 165.5, 158.2,
155.9, 153.0, 151.1, 144.8, 128.3 (2C), 126.7, 126.0 (2C), 125.9 (2C), 120.3, 116.0 (2C),
102.7, 96.3, 49.2, 22.7; IR (neat, cm-1): 3289, 3061, 1601, 698; HRMS (APCI/ASAP, m/z):
332.1396 (calcd. C20H18N3O2, 332.1399, [M+H]+).
4.11.2 (R)-3-(4-((1-Phenylethyl)amino)furo[2,3-d]pyrimidin-6-yl)phenol (6i)
Compound 6i was prepared as described in Section 3.8.1, but starting with compound 6f (150
mg, 0.434 mmol). Silica-gel column chromatography (EtOAc/n-pentane 1/1, Rf = 0.41) and
crystallisation from diethyl ether/n-pentane gave 114 mg (0.354 mmol, 82%) of 6i as a white
solid; mp 130 - 132 °C; HPLC purity: 96%, tR = 26.6 min; [ꢀ]ꢂꢁꢃ = -222.2 (c 1.03, DMSO); 1H
NMR (400 MHz, DMSO-d6) δ: 9.74 (s, 1H), 8.32 - 8.31 (m, 1H), 8.20 (s, 1H), 7.43 - 7.41 (m,
3H), 7.34 - 7.29 (m, 3H), 7.24 - 7.20 (m, 2H), 7.17 - 7.16 (m, 1H), 6.81 - 6.79 (m, 1H), 5.50 -
13
5.43 (m, 1H), 1.55 (d, J = 7.0, 3H); C NMR (100 MHz, DMSO-d6) δ: 165.7, 157.9, 156.2,
153.7, 150.3, 144.7, 130.4, 130.3, 128.3 (2C), 126.7, 126.0 (2C), 115.9, 115.0, 110.6, 102.5,
99.0, 49.3, 22.6; IR (neat, cm-1): 3294, 2973, 1602, 1454, 775; HRMS (APCI/ASAP, m/z):
332.1399 (calcd. C20H18N3O2, 332.1399, [M+H]+).
4.11.3 (R)-2-(4-((1-Phenylethyl)amino)furo[2,3-d]pyrimidin-6-yl)phenol (6j)
Compound 6j was prepared as described in Section 3.8.1, but starting with compound 6g
(150 mg, 0.434 mmol). Purification by silica-gel column chromatography (EtOAc/n-pentane
1/1, Rf = 0.45), and precipitation from diethyl ether/n-pentane gave 110 mg (0.331 mmol,
76%) of 6j as a white solid; mp 156 - 158 °C; HPLC purity: 96%, tR = 27.5 min; [ꢀ]ꢂꢁꢃ = -
1
322.5 (c 1.03, DMSO); H NMR (400 MHz, DMSO-d6) δ: 10.47 (s, 1H), 8.39-8.37 (m, 1H),
8.17 (s, 1H), 7.78 - 7.76 (m, 1H), 7.70 (s, 1H), 7.43 - 7.41 (m, 2H), 7.34 - 7.30 (m, 2H), 7.23
- 7.19 (m, 2H), 7.04 - 7.02 (m, 1H), 6.96 - 6.92 (m, 1H), 5.49 - 5.43 (m, 1H), 1.54 (d, J = 7.1,
3H); 13C NMR (100 MHz, DMSO-d6) δ: 165.3, 156.6, 155.0, 153.8, 148.0, 145.4, 129.3,
128.7 (2C), 127.1, 126.5 (2C), 126.1, 120.1, 116.7, 103.5, 49.7, 23.1; IR (neat, cm-1): 3301,
27

ACCEPTED MANUSCRIPT
3054, 1639, 702; HRMS (APCI/ASAP, m/z): 332.1399 (calcd. C20H18N3O2, 332.1399,
[M+H]+).
4.11.4 (R)-N-(1-Phenylethyl)-6-(4-vinylphenyl)furo[2,3-d]pyrimidin-4-amine (6k)
(R)-6-(4-Bromophenyl)-N-(1-phenylethyl)furo[2,3-d]pyrimidin-4-amine (6d) (786 mg, 2.00
mmol) was mixed with, vinyl MIDA boronate (402 mg, 2.2 mmol, 1.1 eq.), SPhos (82 mg,
0.2 mmol, 0.1 eq.), Pd(OAc)2 (22 mg, 0.1 mmol, 0.05 eq.), K3PO4 (2.54 g, 12 mmol, 6 eq.)
and a degassed solution 1,4-dioxane/water (5/2) (15 mL) under N2 atmosphere. The reaction
mixture was stirred for 3 hours at 95 °C under an N2-atmosphere, diluted with CH2Cl2 (50
mL), cooled to 20 °C and filtered. The filtrate was evaporated to dryness. The residue was
dissolved in CH2Cl2 (100 mL) and washed with water (2 × 50 mL) and brine (50 mL). The
organic phase was dried over Na2SO4 and evaporated. The crude product was purified by
silica-gel chromatography (CH2Cl2/MeOH, 99/1→98/2, Rf = 0.53 (CH2Cl2/MeOH, 94/6)) and
gave 633 mg (1.85 mmol, 93 %) of 6k as white solid; mp 70 - 71 °C, HPLC purity: 97%, tR =
30.1 min; [ꢀ]ꢂꢁꢃ = - 318.2 (c 1.00, DMSO); 1H NMR (400 MHz, CDCl3) δ: 8.38 (s, 1H), 7.72
(d, J = 8.3, 2H), 7.47 - 7.41 (m, 4H), 7.36 (t, J = 7.5, 2H), 7.29 (t, J = 6.9, 1H), 6.78 (s, 1H),
6.72 (dd, J = 17.6, 10.9, 1H), 5.80 (d, J = 17.6, 1H), 5.45 (br. s, 2H), 5.30 (d, J = 11.2, 1H),
1.68 (d, J = 6.6, 3H); 13C NMR (100 MHz, CDCl3) δ: 166.8, 156.6, 153.9, 152.1, 143.5,
138.2, 136.2, 129.0, 128.7 (2C), 127.7, 126.8, 126.13 (2C), 124.9 (2C), 114.8 (2C), 103.1,
97.3, 50.96, 22.9; IR (neat, cm-1): 3265, 3059, 2974, 2927, 1583, 1493, 1448, 1352, 1299,
1138, 781; HRMS (APCI/ASAP, m/z): 342.1602 (calcd. for C22H20N3O: 342.1606) [M+H]+.
4.11.5 (R)-N1,N1-Dimethyl-N2-(4-(4-((1-phenylethyl)amino)furo[2,3-d]pyrimidin-6-
yl)phenyl)ethane-1,2-diamine (6l)
(R)-6-(4-Bromophenyl)-N-(1-phenylethyl)furo[2,3-d]pyrimidin-4-amine (6d) (50.1 mg, 0.127
mmol) was mixed with N1,N1-dimethylethane-1,2-diamine (17 µL, 0.152 mmol, 1.2 eq.),
BrettPhos Pd G1 (2.03 mg, 2.54 µmol, 2 mol%), BrettPhos (1.36 mg, 2.54 µmol, 2 mol%)
and NaOt-Bu (24 mg, 0.254 mmol, 2 eq.) and 1,4-dioxane (1 mL) under N2 atmosphere. The
28