9954
P. Li, J. C. Xu / Tetrahedron 56 (2000) 9949±9955
N-(tert-Butyloxycarbonyl)-leucyl-glycyl-leucyl-glycyl-
valine benzyl ester (Boc-Leu-Gly-Leu-Gly-Val-OBzl).
To a cooled suspension of Boc-Leu-Gly-OH (0.254 g,
0.88 mmol), HCl´Leu-Gly-Val-OBzl (0.331 g, 0.80 mmol)
and CMBI (0.287 g, 0.88 mmol) in 50 mL CH2Cl2, DIEA
(0.45 mL, 2.56 mmol) was added at 2108C. The reaction
mixture was stirred at room temperature for 1 h. Yield:
0.488 g (94.2%), mp 146±1478C, Rf 0.71 (AcOEt), [a]2D2
219.7 (c 1 CHCl3); [Found: C, 60.31; H, 8.35; N, 10.66.
C33H53N5O8´0.5H2O requires C, 60.35; H, 8.29; N, 10.66%];
more than two conformers d0.82±1.10 (m, 6H, 2g-CH3-
Val), 1.45, 1.46, 1.49 (3s, 9H, But), 1.71±2.45 (m, 5H,
g-CH2-Pro, b-CH-Val, b-CH2-Pro), 2.99±3.41 (multi s,
3H, N-CH3-Sar), 3.52±3.89 (2m, 2H, d-CH2-Pro),
4.10±4.92 (m, 7H, 9-CH-Fluorenyl, CH2-Fmoc, a-CH2-
Sar, a-CH-Pro, a-CH-Val), 5.31, 5.56 (2d, J9.3 Hz, 1H,
NH-Val), 7.27 (t, J7.3 Hz, 2H, 2,7-CH-Fluorenyl), 7.37 (t,
J7.3 Hz, 2H, 3,6-CH-Fluorenyl), 7.63 (m, 2H, 1,8-CH-
Fluorenyl), 7.76 (d, J7.4 Hz, 2H, 4,5-CH-Fluorenyl);
EIMS m/z: 564 [M1H]1, 419 [M2Sar-OBut]1, 322
[M2Pro-Sar-OBut]1, 179 [Fmoc-CO2]1, 57 [But]1.
n
max(KBr) 3299vs, 2960s, 1730sh, 1633vs, 1533vs, 1368m,
1248s, 1168s, 1047w, 698w cm21; H NMR (400 MHz,
CDCl3): d0.72±1.06 (m, 18H, 4d-CH3-Leu, 2g-CH3-
Val), 1.42 (s, 9H, But), 1.14±1.98 (m, 6H, 2b-CH2-Leu,
2g-CH-Leu), 2.19 (m, 1H, b-CH-Val), 3.85±4.28 (m, 5H,
2a-CH2-Gly, a-CH-Leu), 4.59 (dd, J8.6 Hz, J05.2 Hz,
1H, a-CH-Val), 4.72 (m, 1H, a-CH-Leu), 5.10, 5.21 (AB,
J12.2 Hz, 2H, CH2-OBzl), 5.55 (br, 1H, NH-Gly), 7.34 (s,
5H, Ph-OBzl), 7.48 (br, 1H, NH-Leu), 7.62 (br, 1H, NH-
Val), 7.67 (br, 1H, NH-Gly), 7.81 (br, 1H, NH-Leu); ESIMS
m/z: 1965 [M1M1M1Na]1, 1319 [M1M1Na]1, 984
[(M1M1M1Na1H)/2]1, 671 [M1Na]1, 648 [M1H]1.
1
N-[(9H-Fluoren-9-ylmethoxy)carbonyl]-threonyl-d-valyl-
prolyl-sarcosine tert-butyl ester (Fmoc-Thr-d-Val-Pro-
Sar-OBut, 8). Compound 7 (0.409 g, 0.726 mmol) was
deprotected according to the above experimental procedure
to give H-d-Val-Pro-Sar-OBut, which was further dried in
vacuo for 2 h and participated the following coupling
reaction without puri®cation. To a cooled solution of
Fmoc-Thr-OH (0.297 g, 0.871 mmol), CMBI (0.284 g,
0.871 mmol) and the above H-d-Val-Pro-Sar-OBut in
3 mL CH2Cl2, DIEA (0.43 mL, 2.47 mmol) was added.
The reaction mixture was stirred at room temperature for
1 h. Yield: 0.446 g (92.5%), mp 96±978C, Rf 0.34 (CHCl3/
CH3OH: 20/1), [a]2D3224.6 (c 1, CHCl3); [Found: C,
64.06; H, 7.53; N, 8.61. C36H48N4O8´0.5H2O requires C,
64.17; H, 7.33; N, 8.32%]; nmax(KBr) 3318s, 2975m,
2877sh, 1739vs, 1668sh, 1644vs, 1450s, 1232s, 1159m,
Synthesis of the hindered depsipeptide moiety of Actino-
mycin D using reagent CMBI N-[(9H-Fluoren-9-yl-
methoxy)carbonyl]-prolyl-sarcosine tert-butyl ester
(Fmoc-Pro-Sar-OBut, 6). To a cooled solution of Sar-
OBut (0.798 g, 5.5 mmol), Fmoc-Pro-OH (1.69 g, 5.0
mmol) and CMBI (1.80 g, 5.5 mmol) in 5 mL CH2Cl2,
DIEA (1.83 mL, 10.5 mmol) was added at 2108C. The
reaction mixture was stirred at room temperature for 1 h.
Yield: 2.28 g (98.2%), Rf 0.28 (AcOEt/PE: 1/2), [a]2D3
761sh, 742m cm21 1H NMR (300 MHz, CDCl3) two
;
conformers d0.85±1.04 (m, 6H, 2g-CH3-Val), 1.23 (d,
J7.8 Hz, 3H, g-CH3-Thr), 1.46, 1.49 (2s, 9H, But),
1.76±2.49 (m, 5H, g-CH2-Pro, b-CH-Val, b-CH2-Pro),
2.95, 3.13 (2s 1: 4.6, 3H, N-CH3-Sar), 3.34±4.66 (m, 11H,
d-CH2-Pro, 9-CH-Fluorenyl, CH2-Fmoc, a-CH2-Sar, a-CH-
Pro, a-CH-Val, a-CH-Thr, b-CH-Thr), 6.02 (br, 1H,
OH-Thr), 4.86, 6.85 (2m, 2H, NH-Val, NH-Thr), 7.34 (t,,
J7.3 Hz, 2H, 2,7-CH-Fluorenyl), 7.41 (t,, J7.3 Hz, 2H,
3,6-CH-Fluorenyl), 7.64 (d, J7.3 Hz, 2H, 1,8-CH-Fluor-
enyl), 7.78 (d, J7.3 Hz, 2H, 4,5-CH-Fluorenyl); EIMS
m/z: 664 M1z, 324 [M-d-Val-Pro-Sar-OBut]1, 179 [Fmoc-
CO2]1, 57 [But]1.
1
236.2 (c 1, CHCl3); H NMR (300 MHz, CDCl3) four
conformers d1.43, 1.46, 1.49 (3s, 9H, But), 1.70±2.35
(m, 4H, g-CH2-Pro, b-CH2-Pro), 2.86, 3.01, 3.15, 3.38
(4S, 3H, N-CH3-Sar), 3.45±3.88 (2m, 2H, d-CH2-Pro),
4.10±4.92 (m, 6H, 9-CH-Fluorenyl, CH2-Fmoc, a-CH2-
Sar, a-CH-Pro), 7.31 (t, J7.3 Hz, 2H, 2, 7-CH-Fluorenyl),
7.40 (t, J7.3 Hz, 2H, 3, 6-CH-Fluorenyl), 7.63 (m, 2H,
1,8-CH-Fluorenyl), 7.73 (d, J7.3 Hz, 2H, 4,5-CH-Fluor-
enyl); EIMS m/z: 391 [M2OBut]1, 179 [Fmoc-CO2]1, 57
[But]1.
O-[N-Benzyloxycarbonyl-N-methylvalyl]-N-[(9H-Fluoren-
9-ylmethoxy)carbonyl]-threonyl-d-valyl-prolyl-sarcosine
tert-butyl ester (Fmoc-Thr(OMeVal-Z)-d-Val-Pro-Sar-
OBut, 9). Compound 8 (0.532 g, 0.80 mmol), Z-MeVal-
OH(0.318 g, 1.20 mmol), DMAP (98 mg, 0.8 mmol) and
CMBI (0.392 g, 1.20 mmol) was dissolved in 10 mL
CH2Cl2, then DIEA (0.28 mL, 1.6 mmol) was added at
2108C. The reaction mixture was stirred at room tempera-
ture for 4 h. Yield: 0.652g (89.3%), mp 92±92.58C, Rf 0.44
(CHCl3/CH3OH: 20/1), [a]2D3222.6 (c 1, CHCl3); [Found:
C, 64.78; H, 7.19; N, 7.36. C50H65N5O11´H2O requires C,
64.57; H, 7.26; N, 7.53%]; nmax(KBr) 3298s, 2972s, 1740vs,
1705sh, 1673sh, 1624sh, 1500m, 1451s, 1231m, 1157s,
N-[(9H-Fluoren-9-ylmethoxy)carbonyl]-d-valyl-prolyl-
sarcosine tert-butyl ester (Fmoc-d-Val-Pro-Sar-OBut, 7).
Compound 6 (2.14 g, 4.61 mmol) was dissolved in 15 mL
CH3CN, and treated with diethylamine (5 mL) under nitro-
gen atmosphere until TLC analysis indicated the starting
material disappeared (ca. 40 min). The solution was concen-
trated in vacuo, the residue was dissolved in CH3CN and
concentrated again to give N-Fmoc-deprotected peptide,
which was further dried in vacuo for 2 h and utilized for
the following coupling reaction without further puri®cation.
CMBI (1.66 g, 5.07 mmol), Fmoc-d-Val-OH (1.72 g,
5.07 mmol) and the above residue were dissolved in 6 mL
CH2Cl2, then DIEA (2.57 mL, 14.8 mmol) was added at
2108C. The reaction mixture was stirred at room tempera-
ture for 1 h. Yield: 2.04 g (78.5%), mp 72±738C, Rf 0.57
(CHCl3/CH3OH: 20/1), [a]2D1219.0 (c 0.5, CHCl3);
[Found: C, 67.24; H, 7.25; N, 7.03. C32H41N3O6´0.5H2O
requires C, 67.11; H, 7.39; N, 7.33%]; nmax(KBr) 3285m,
2975s, 1740vs, 1720sh, 1647vs, 1450s, 1232s, 1159s,
1
1054m, 760sh, 741m cm21; H NMR (400 MHz, CDCl3)
more than three conformers d0.77±1.08 (m, 12H,
4g-CH3 of D-Val, MeVal), 1.24 (m, 3H, g-CH3-Thr),
1.41, 1.45, 1.47 (3s, 9H, But), 1.76±2.47 (m, 6H, g-CH2-
Pro, b-CH-d-Val, b-CH-MeVal, b-CH2-Pro), 2.81±3.13
(m, 6H, N-CH3-Sar, N-CH3-MeVal), 3.23, 4.59 (2m, 2H,
a-CH2-Sar), 3.52±3.73 (m, 2H, d-CH2-Pro), 3.76±4.92
(m, 7H, a-CH-Thr, 9-CH-Fluorenyl, CH2-Fmoc, a-CH-Pro,
1
1116m, 1029m, 742s cm21; H NMR (300 MHz, CDCl3)