The Journal of Organic Chemistry
Page 6 of 12
2H), 4.57 (dd, J = 8.5, 5.7 Hz, 1H), 4.44 (dd, J = 9.8, 5.1 Hz, with Parafilm M®. The flask was placed under vacuum for 5 min
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1H), 4.04 (dd, J = 9.9, 5.3 Hz, 1H), 3.87 (d, J = 16.8 Hz, 1H),
3.74 (d, J = 16.5 Hz, 1H), 3.68 (s, 3H), 3.07 (dd, J = 14.1, 5.7
Hz, 1H), 2.83 (dd, J = 14.1, 8.6 Hz, 1H), 1.72 – 1.49 (m, 6H),
1.44 (s, 9H), 1.01 – 0.83 (m, 12H); 13C{1H} NMR (151 MHz,
CD3OD) δ 176.3, 174.2, 173.5, 171.2, 158.1, 157.3, 131.3,
128.9, 116.2, 80.7, 56.1, 54.8, 52.7, 52.2, 43.5, 41.9, 41.5, 38.0,
28.8, 25.9, 25.8, 23.5, 23.3, 21.9, 9; IR (FT-ATR, cm-1, neat) νmax
3296, 2957, 1644, 1515, 1439, 1367, 1234, 1161, 1022, 827;
HRMS m/z [M+H]+ calcd for C29H46N4O8 579.3388, found
579.3389 (ES+).
and backfilled with N2. This process was repeated two
additional times. Solvent (32 mL, 2.5 mM) was added through
the septum, and the mixture was allowed to stir for 15 h at 45 °C
in an oil bath. The mixture was diluted with EtOAc and
transferred to a separatory funnel. The organic layer washed
with a solution of saturated NH4Cl (aq). The organic layer was
separated and the aqueous layer was extracted with EtOAc
again. The organic layer was washed three times with brine. The
combined organic layers were then dried over anhydrous
Na2SO4, filtered, and concentrated in vacuo. The crude residue
was then dissolved in 10 mL of DMSO. 1 mL of DMSO was
then added which contained a known amount of di-tert-
butylbiphenyl to serve as an internal standard (0.0536 g in 100
mL). An aliquot was then submitted for analysis by LC-MS.
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Boc-Leu-Val-Tyr-Leu-OMe (1c) was synthesized following
the Solution-phase peptide coupling procedure followed by
Procedure 1. The crude material was then purified by reversed-
phase chromatography (20 à 100% MeOH/H2O) to provide
1
the desired product as a white solid (42% yield). H NMR (600
Procedure 3: Synthesis of authentic products for
monotyrosine containing compounds. To an oven dried 10-
mL Schlenk flask equipped with a magnetic stir bar was added
tyrosine-containing peptide (0.10 mmol, 1.00 equiv), N-(2-
bromophenyl)-2,2,2-trifluoroacetamide (0.0300 g, 0.11 mmol,
1.10 equiv), Cu(MeCN)4BF4 (0.0064 g, 0.02 mmol, 0.20
equiv), N,N-dimethylglycine (0.0037 g, 0.02 mmol, 0.20
equiv), and Cs2CO3 (0.1300 g, 4.00 mmol, 4.00 equiv) which
was flame dried under vacuum before use. The flask was sealed
with a new rubber septum and further secured with Parafilm M®.
The flask was placed under vacuum for 5 min and backfilled
with N2. This process was repeated two additional times. THF
(2.5 mL, 0.04 M w.r.t. tyrosine-containing peptide) was added
through the septum, and the mixture was allowed to stir for 15 h
at 45 °C in an oil bath. Reaction mixture was diluted with
EtOAc and transferred to a separatory funnel. The organic layer
was washed with a solution of saturated NH4Cl (aq). The
organic layer was separated and the aqueous layer was extracted
with EtOAc again. The organic layer was washed three times
with brine. The combined organic layer was then dried over
anhydrous Na2SO4, filtered, and concentrated in vacuo. The
crude material was purified by reversed-phase chromatography.
Boc-Leu-Asp-Tyr(O-(2-(2,2,2-
MHz, CD3OD) δ 7.02 (d, J = 8.0 Hz, 2H), 6.77 – 6.57 (m, 2H),
4.56 (t, J = 7.4 Hz, 1H), 4.42 (dd, J = 10.0, 5.1 Hz, 1H), 4.15 (d,
J = 6.9 Hz, 1H), 4.06 (t, J = 7.7 Hz, 1H), 3.63 (s, 3H), 2.99 (dd,
J = 14.0, 6.6 Hz, 1H), 2.79 (dd, J = 14.0, 8.0 Hz, 1H), 1.99 (h, J
= 6.9 Hz, 1H), 1.70 – 1.50 (m, 4H), 1.48 (t, J = 7.4 Hz, 2H),
1.42 (s, 9H), 0.93 (d, J = 6.6 Hz, 3H), 0.90 (dt, J = 6.8, 1.7 Hz,
6H), 0.86 (t, J = 5.4 Hz, 9H); 13C{1H} NMR (151 MHz,
CD3OD) δ 175.6, 174.1, 173.3, 173.0, 157.2, 131.3, 128.7,
116.2, 80.7, 59.7, 55.9, 54.6, 52.7, 52.0, 41.7, 41.6, 38.0, 32.4,
28.7, 25.9, 25.7, 23.5, 23.4, 21.9, 21.8, 19.7, 18.5; IR (FT-ATR,
cm-1, neat) νmax 3277, 2957, 1639, 1514, 1367, 1234, 1167,
1046, 1020, 827, 663; HRMS m/z [M+H]+ calcd for
C32H52N4O8 621.3858, found 621.3865.
Boc-Leu-Phe-Tyr-Leu-OMe (1d) was synthesized following
the Solution-phase peptide coupling procedure followed by
Procedure 1. The crude material was then purified by reversed-
phase chromatography (20 à100% MeOH/H2O) to provide
1
the desired product as a white solid (51% yield). H NMR (600
MHz, CD3OD) δ 7.22 – 7.21 (m, 2H), 7.18 –7.16 (m, 3H),
7.02 (d, J = 8.0 Hz, 2H), 6.68 (d, J = 8.2 Hz, 2H), 4.58 (dd, J =
8.5, 5.5 Hz, 1H), 4.54 (t, J = 7.1 Hz, 1H), 4.44 (dd, J = 9.5, 5.6
Hz, 1H), 3.99 (dd, J = 9.3, 5.9 Hz, 1H), 3.65 (s, 3H), 3.06 (dd, J
= 14.0, 5.5 Hz, 1H), 3.00 (dd, J = 14.0, 6.3 Hz, 1H), 2.87 (dd, J
= 14.0, 8.4 Hz, 1H), 2.81 (dd, J = 14.0, 7.9 Hz, 1H), 1.69 – 1.54
(m, 4H), 1.42–1.31 (m, 12H), 1.38 – 1.31 (4H), 0.91 (td, J =
22.3, 20.7, 6.5, 1.2 Hz, 12H); 13C{1H} NMR (151 MHz,
CD3OD): δ 175.4, 174.2, 173.2, 172.8, 157.9, 157.3, 138.1,
131.4, 130.4, 129.4, 128.7, 127.7, 116.2, 80.7, 56.0, 55.5, 54.7,
52.7, 52.1, 42.0, 41.6, 38.8, 38.1, 28.8, 25.9, 25.8, 23.4, 23.3,
22.0, 21.9; IR (FT-ATR, cm-1, neat) νmax 3282, 2955, 1640, 1515,
1367, 1230, 1166, 1022, 829, 697; HRMS m/z [M+H]+ calcd
for C36H52N4O8 669.3858, found 669.3857 (ES+).
Procedure 2: Procedures for competition experiment
between tetrapeptides. To an oven dried 50 mL Schlenk flask
equipped with a magnetic stir bar was added 1a (0.020
mmol, 1.00 equiv), 1b (0.020 mmol, 1.00 equiv), 1c (0.020
mmol, 1.00 equiv), 1d (0.020 mmol, 1.00 equiv) N-(2-
bromophenyl)-2,2,2-trifluoroacetamide (0.0054 g, 0.020 mmol,
1.00 equiv), Cu source (0.008 mmol, 0.40 equiv), ligand (0.016
mmol, 0.80 equiv), and base (0.064 mmol, 3.20 equiv). The
flask was sealed with a new rubber septum and further secured
trifluoroacetamido)phenoxy)-Leu-OMe
(2a)
was
synthesized following Procedure 3 from 1a. The crude material
was then purified by reversed-phase chromatography (20
à100% MeOH/H2O) to provide the desired product as a
white solid (43% yield). 1H NMR (600 MHz, CD3OD) δ 7.65
(dd, J = 8.0, 1.6 Hz, 1H), 7.27 – 7.23 (m, 3H), 7.15 (td, J = 7.7,
1.4 Hz, 1H), 6.96 – 6.94 (m, 3H), 4.63 (t, J = 6.3 Hz, 1H), 4.58
(dd, J = 8.2, 5.7 Hz, 1H), 4.44 (dd, J = 9.9, 4.9 Hz, 1H), 4.02 (t,
J = 8.9, 1H), 3.65 (s, 3H), 3.16 (dd, J = 14.1, 5.4 Hz, 1H), 2.95
(dd, J = 14.1, 8.2 Hz, 1H), 2.80 (dd, J = 17.1, 6.3 Hz, 1H), 2.71
(dd, J = 17.1, 6.4 Hz, 1H), 1.72 – 1.61 (m, 3H), 1.61 – 1.52 (m,
1H), 1.52 – 1.45 (m, 2H), 1.42 (s, 9H), 0.96 – 0.84 (m, 12H);
13C{1H} NMR (151 MHz, CD3OD) 175.8, 174.2, 173.0, 172.5,
158.2, 157.3 (d, J = 37.1 Hz), 156.5, 152.2, 134.2, 131.9, 129.3,
127.2, 124.4, 120.1, 119.6, 117.5 (d, J = 287.4 Hz), 80.8, 56.1,
54.8, 52.7, 52.2, 51.3, 41.8, 41.4, 37.8, 36.2, 28.8, 25.9, 25.8,
23.5, 23.4, 21.9, 21.8; 19F NMR (376 MHz, CD3OD) δ –77.98;
IR (FT-ATR, cm-1, neat) νmax 2958, 1734, 1646, 1504, 1457,
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