4248 J . Org. Chem., Vol. 67, No. 12, 2002
Avenoza et al.
mg (99%) of 3 as a white solid (mp ) 36-38 °C). Rf ) 0.52
DMAP (1 mg) were added, at 0 °C, under an inert atmosphere.
The mixture was allowed to warm at room temperature, and,
after stirring for 3 h, the reaction was washed with water (2
× 10 mL). The organic layer was dried over anhydrous Na2-
SO4, filtered, and evaporated to give a residue that was
purified by silica gel column chromatography, eluting with
MeOH/EtOAc (5:95) to yield 145 mg (86%) of 19 as a white
(MeOH/EtOAc, 1:4). [R]25 (c 0.91, CHCl3) ) -2.5. ESI + (m/
D
z) ) 326.2. IR (CH2Cl2, cm-1): 3444, 3422, 3340, 1667, 1633.1H
NMR (CDCl3): δ 1.18 (s, 9H), 1.53-2.02 (m, 7H), 2.13-2.26
(m, 1H), 2.69 (d, 3H, J ) 4.8 Hz), 3.61 (dd, 1H, J ) 11.4 Hz,
J ) 3.6 Hz), 4.11 (‘t’, 1H, J ) 6.0 Hz), 4.23 (dd, 1H, J ) 11.4
Hz, J ) 2.7 Hz), 4.39-4.49 (m, 1H), 4.52-4.62 (m, 1H), 6.51
(d, 1H, J ) 8.4 Hz), 7.84-8.01 (m, 1H). 13C NMR (CDCl3): δ
26.2, 28.0, 30.3, 30.8, 30.9, 33.1, 40.2, 54.6, 60.2, 62.2, 69.9,
170.7, 171.4, 181.7. Anal. Calcd for C16H27N3O4: C, 59.06; H,
8.36; N, 12.91. Found: C, 58.98; H, 8.31; N, 12.99.
solid (mp ) 28-30 °C). Rf ) 0.2 (MeOH/EtOAc, 5:95) [R]23 (c
D
0.95, CHCl3) ) +7.4. ESI + (m/z) ) 416.6. IR (CH2Cl2, cm-1):
3469, 3436, 1681, 1658.1H NMR (CDCl3): δ 1.12 (s, 9H), 1.31-
1.57 (m, 2H), 1.58-1.82 (m, 4H), 1.83-2.11 (m, 2H), 2.70 (d,
3H, J ) 4.8 Hz), 3.52-3.65 (m, 2H), 4.26-4.34 (m, 1H), 4.40
(d, 1H, J ) 12.0 Hz), 4.50 (d, 1H, J ) 12.0 Hz), 4.74-4.83 (m,
1H), 6.26-6.35 (m, 1H), 6.61 (d, 1H, J ) 7.2 Hz), 7.14-7.32
(m, 5H).13C NMR (CDCl3): δ 26.2, 27.2, 29.1, 30.6, 30.8, 35.2,
38.5, 51.4, 60.0, 69.5, 70.4, 73.2, 127.7, 127.8, 128.3, 137.3,
170.8, 170.9, 178.1. Anal. Calcd for C23H33N3O4: C, 66.48; H,
8.00; N, 10.11. Found: C, 66.56; H, 7.91; N, 10.06.
Boc-Ah c-OH (15). Boc-Ahc-OBn (9) (570 mg, 1.72 mmol)
in MeOH (25 mL) was hydrogenated, using 70 mg of 10%
Pd-C as a catalyst, at room temperature for 3 h. The catalyst
and the solvent were removed to give quantitatively 15 as a
white solid (mp ) 54-56 °C). ESI - (m/z) ) 240.1. IR (CH2-
Cl2, cm-1): 1692, 1599. 1H NMR (CDCl3): δ 1.19-1.38 (m,
11H), 1.51-1.77 (m, 4H), 1.99-2.18 (m, 2H), 4.09-4.18 (m,
1H). 13C NMR (CDCl3): δ 28.3, 29.2, 34.0, 59.7, 70.7, 80.7,
156.9, 178.4. Anal. Calcd for C12H19NO4: C, 59.73; H, 7.94; N,
5.81. Found: C, 59.80; H, 7.92; N, 5.89.
P iv-L-Ser -Ah c-NHMe (4). A solution of Piv-L-Ser(OBn)-
Ahc-NHMe (19) (90 mg, 0.22 mmol) in MeOH (20 mL) was
hydrogenated, using 50 mg of 10% Pd-C as a catalyst, at room
temperature for 2 h. The catalyst and the solvent were
removed, and the residue was purified by silica gel column
chromatography, eluting with MeOH/EtOAc (1:9) to give 65
mg (99%) of 4 as a white solid (mp ) 53-55 °C). Rf ) 0.15
Boc-Ah c-NHMe (16). A solution of Boc-Ahc-OH (15) (246
mg, 1.02 mmol) in CH3CN (10 mL) was treated with DIEA
(0.9 mL, 5.10 mmol), methylamine hydrochloride (138 mg, 2.04
mmol), and TBTU (393 mg, 1.22 mmol) under an inert
atmosphere. The reaction mixture was stirred at room tem-
perature for 16 h and partitioned between brine (8 mL) and
EtOAc (20 mL). The organic layer was washed with 0.1 N HCl
(2 × 10 mL) and 5% NaHCO3 (2 × 10 mL), dried over
anhydrous Na2SO4, filtered, and evaporated to give a residue
that was purified by silica gel column chromatography, eluting
with EtOAc, to yield 230 mg (88%) of 16 as a white solid (mp
) 89-91 °C). Rf ) 0.40 (EtOAc). ESI + (m/z) ) 255.4. IR (CH2-
Cl2, cm-1): 3444, 1702, 1681. 1H NMR (CDCl3): δ 1.35 (s, 9H),
1.38-1.49 (m, 2H), 1.72-1.91 (m, 4H), 1.92-2.07 (m, 2H), 2.80
(MeOH/EtOAc, 1:9). [R]25 (c 0.94, CHCl3) ) -0.3. ESI + (m/
D
z) ) 326.4. IR (CH2Cl2, cm-1): 3685, 3602, 3446, 3406, 1681,
1658.1H NMR (CDCl3): δ 1.14 (s, 9H), 1.49-1.64 (m, 2H),
1.67-1.90 (m, 3H), 1.91-2.16 (m, 3H), 2.82 (d, 3H, J ) 4.8
Hz), 3.71 (dd, 1H, J ) 11.4 Hz, J ) 4.5 Hz); 3.80 (dd, 1H, J )
11.4, J ) 4.2 Hz), 4.38-4.47 (m, 1H), 4.61-4.69 (m, 1H), 6.21-
6.34 (m, 1H), 6.82 (d, 1H, J ) 6.9 Hz).13C NMR (CDCl3): δ
26.7, 27.4, 29.6, 30.8, 35.2, 35.3, 38.7, 53.6, 59.8, 64.8, 69.4,
171.0, 171.0, 179.0. Anal. Calcd for C16H27N3O4: C, 59.06; H,
8.36; N, 12.91. Found: C, 59.17; H, 8.52; N, 12.83.
(d, 3H, J ) 4.8 Hz), 4.21-4.30 (m, 1H), 5.99-6.11 (m, 1H).13
C
NMR (CDCl3): δ 26.1, 27.9, 28.9, 34.0, 60.3, 70.4, 80.5, 157.0,
172.2. Anal. Calcd for C13H22N2O3: C, 61.39; H, 8.72; N, 11.01.
Found: C, 61.41; H, 8.62; N, 11.13.
P r ep a r a tion of MTP A Ester s. A solution of MTPA (0.071
mmol) in CH2Cl2 (1 mL) was added to a solution of the peptide
(0.062 mmol), DCC (0.068 mmol), and DMAP (0.062 mmol) in
CH2Cl2 (1.0 mL). The mixture was stirred at room temperature
for 4.5 h. The resulting white suspension was filtered to
remove the N,N′-dicyclohexylurea. The filtrate was concen-
trated to give a white slurry, to which Et2O was added. The
resulting suspension was filtered to remove the N-acyl-N′-
cyclohexylurea and then concentrated to give the crude
product, which was purified by column chromatography on
silica gel, eluting with MeOH/EtOAc (5:95).
Ah c-NHMe.HCl (17). Boc-Ahc-NHMe (16) (230 mg, 0.90
mmol) was dissolved in 10 mL of 1 N HCl-THF (3:7) and the
mixture was stirred at room temperature for 1.5 h. The solvent
was evaporated in vacuo to give quantitatively 17 as a white
solid (mp > 200 °C).1H NMR (CD3OD): δ 1.82-2.26 (m, 8H),
2.80 (s, 3H), 4.13-4.22 (m, 1H).13C NMR (CD3OD): δ 26.5,
29.2, 31.7, 59.1, 74.7, 170.1. Anal. Calcd for C8H15N2OCl: C,
50.39; H, 7.93; N, 14.69. Found: C, 50.47; H, 7.82; N, 14.81.
Boc-L-Ser (OBn )-Ah c-NHMe (18). A solution of Boc-L-Ser-
(OBn)-OH (5) (94 mg, 0.32 mmol) in CH3CN (4 mL) was
treated with DIEA (0.23 mL, 1.31 mmol), Ahc-NHMe‚HCl 17
(50 mg, 0.26 mmol) and TBTU (104 mg, 0.32 mmol) under an
inert atmosphere. The reaction mixture was stirred at room
temperature for 16 h and partitioned between brine (4 mL)
and EtOAc (10 mL). The organic layer was washed with 0.1
N HCl (2 × 5 mL) and 5% NaHCO3 (2 × 5 mL), dried over
anhydrous Na2SO4, filtered and evaporated to give a residue
that was purified by silica gel column chromatography, eluting
with EtOAc, to yield 98 mg (87%) of 18 as a white solid (mp )
P iv-L-Ser (O-(+)-MTP A)-L-P r o-NHMe (20). 82% yield as
a white solid (mp ) 42-44 °C). Rf ) 0.38 (MeOH/EtOAc, 5:95).
[R]27 (c 0.79, CHCl3) ) -21.0. ESI + (m/z) ) 516.6. IR (CH2-
D
Cl2, cm-1): 3434, 3357, 1753, 1671, 1654. NMR data for the
major conformer: 1H NMR (CDCl3): δ 1.16 (s, 9H), 1.85-2.14
(m, 3H), 2.32-2.43 (m, 1H), 2.66 (d, 3H, J ) 4.8 Hz), 3.54 (s,
3H), 3.61-3.70 (m, 2H), 4.44-4.57 (m, 2H), 4.69 (dd, 1H, J )
11.4 Hz, J ) 4.2 Hz), 4.98-5.06 (m, 1H), 6.46-6.54 (m, 1H),
6.62 (d, 1H, J ) 7.2 Hz), 7.38-7.51 (m, 5H). 19F NMR
(CDCl3): δ -78.81. 13C NMR (CDCl3): δ 25.6, 26.1, 27.2, 27.8,
38.7, 47.6, 50.0, 55.5, 60.8, 64.5, 121.2, 125.0, 127.3, 128.6,
129.8, 131.6, 167.0, 168.9, 170.9, 178.3. Anal. Calcd for
38-40 °C). Rf ) 0.24 (EtOAc). [R]22 (c 0.98, CHCl3) ) +1.9.
D
ESI + (m/z) ) 432.5. IR (CH2Cl2, cm-1): 3470, 3429, 1710,
1681, 1671.1H NMR (CDCl3): δ 1.35 (s, 9H), 1.43-2.05 (m,
8H), 2.69 (d, 3H, J ) 4.8 Hz), 3.52-3.64 (m, 2H), 4.25-4.35
(m, 1H), 4.39 (d, 1H, J ) 12.0 Hz), 4.42-4.58 (m, 2H), 5.40 (d,
1H, J ) 8.1 Hz), 6.27-6.36 (m, 1H), 7.14-7.29 (m, 5H). 13C
NMR (CDCl3): δ 26.3, 28.2, 29.3, 30.6, 31.3, 35.0, 52.7, 60.0,
69.7, 70.9, 73.3, 79.8, 127.6, 127.7, 128.2, 137.4, 155.2, 171.1,
171.2. Anal. Calcd for C23H33N3O5: C, 64.02; H, 7.71; N, 9.74.
Found: C, 64.08; H, 7.63; N, 9.68.
C
24H32F3N3O6: C, 55.92; H, 6.21; N, 8.16. Found: C, 55.83; H,
6.18; N, 8.12.
P iv-L-Ser (O-(-)-MTP A)-L-P r o-NHMe (23). 87% yield as
a white solid (mp ) 47-49 °C). Rf ) 0.46 (MeOH/EtOAc, 5:95).
[R]21 (c 0.81, CHCl3) ) -71.9. ESI + (m/z) ) 516.6. IR (CH2-
D
Cl2, cm-1): 3434, 3357, 1754, 1672, 1650. NMR data for the
major conformer: 1H NMR (CDCl3): δ 1.14 (s, 9H), 1.83-2.11
(m, 3H), 2.34-2.45 (m, 1H), 2.73 (d, 3H, J ) 4.8 Hz), 3.52 (s,
3H), 3.55-3.76 (m, 2H), 4.53-4.61 (m, 2H), 4.69 (dd, 1H, J )
11.4 Hz, J ) 4.2 Hz), 4.94-5.05 (m, 1H), 6.51-6.64 (m, 2H),
7.39-7.53 (m, 5H). 19F NMR (CDCl3): δ -71.77. 13C NMR
(CDCl3): δ 24.9, 26.1, 27.2, 27.8, 38.7, 47.5, 49.9, 55.3, 60.9,
64.3, 121.2, 125.0, 127.2, 128.6, 129.8, 131.8, 166.8, 168.9,
170.9, 178.3. Anal. Calcd for C24H32F3N3O6: C, 55.92; H, 6.21;
N, 8.16. Found: C, 55.81; H, 6.15; N, 8.10.
P iv-L-Ser (OBn )-Ah c-NH Me (19). Boc-L-Ser(OBn)-Ahc-
NHMe (18) (175 mg, 0.41 mmol) was dissolved in 10 mL of 1
N HCl/THF (3:7), and the solution was stirred at room
temperature for 15 min. The solvent was evaporated in vacuo
to give quantitatively the corresponding hydrochloride deriva-
tive. This compound was suspended in CH2Cl2 (15 mL), and
DIEA (0.13 mL, 0.90 mmol), PivCl (0.06 mL, 0.49 mmol), and