Molecules 2020, 25, 1557
17 of 25
1
(
NH), 1747 (C=O), 1686 (br C=O), 1522 (NH bend), 1175 (C-O), 1148 (C-O); H NMR (300 MHz, CDCl )
3
2
2
δ
1
H
=
H
1.40 (9H, s, C(CH
3)
3
), 2.87 (3H, s, NCH
3
-8), 3.80 (1H, d, JH-H = 15.0 Hz, CHa/b-6), 3.82 (1H, d, JH-H
=
5.0 Hz, CHa/b-6), 3.83 (1H, dd, JH-H = 12.0 Hz, 3JH-H = 3.0 Hz, CHa/b-3), 3.94 (1H, dd, 2JH-H = 12.0 Hz, JH-
2
3
2
2
= 3.0 Hz, CHa/b-3), 4.91–4.96 (1H, m, CH-2), 5.13 (1H, d, JH-H = 12.0 Hz, OCHa/bAr), 5.18 (1H, d, JH-H
3
13
12.0 Hz, OCHa/bAr), 6.97 (1H, d, JH-H = 6.0 Hz, NH-4), 7.26–7.30 (5H, m, 5 x CHAr); C NMR (75
) δ 28.2 (C(CH ), 35.6 (NCH -8), 44.9 (CH -3), 53.0 (CH -6), 53.0 (CH-2), 68.0 (OCH Ar),
), 128.4 (CHAr), 128.6 (CHAr), 128.7 (CHAr), 134.8 (CHAr quat.), 154.5 (C=O-9), 168.4 (C=O-
MHz, CDCl
3
C
3)
3
3
2
2
2
8
1
3
1.0 (C(CH
3
)
3
+
+
35
37
), 169.4 (C=O-5); HRMS (NSI) calcd for (C18
H26ClN
2O5
) , MH : 385.1525 ( Cl), 387.1496 ( Cl), found
35
37
85.1527 ( Cl), 387.1498 ( Cl). LCMS purity >95% (C-18 reversed phase, MeOH–H O).
2
Tert-butyl ((2R)-3-chloro-1-((1-(diethoxyphosphoryl)ethyl) amino)-1-oxopropan-2-yl)carbamate or Boc-β-
chloro-L-Ala-D/L-Fos diethyl ester (19e). General peptide coupling method was followed, using (R)-2-
(
1
(tert-butoxycarbonyl)amino)-3-chloropropanoic acid (13) (6.0 mmol, 1.34 g) in dry THF and diethyl
-aminoethylphosphonate (9) (6.0 mmol, 1.09 g) in dry THF. The light yellow crude liquid was
purified by column chromatography, using 100% petrol and increasing to 100% ethyl acetate, to
afford 19e as colorless syrup composed of 2 diastereoisomers, Boc-β-Cl-L-Ala-L-Fos diethyl ester and
−
1
Boc-β-Cl-L-Ala-D-Fos diethyl ester (2.03 g, 5.2 mmol, 88%); ῡmax/cm 3261 (NH), 1713 (C=O), 1670
1
(
C=O), 1517 (NH bend), 1225 (P=O), 1164 (C-O), 1020 (P-O-C), 970 (P-O-C); H NMR (300 MHz, CDCl
3
)
2
3
δ
6
4
H
1.15–1.46 (9H, m, CH
3
-2, 2 × OCH
2
CH
3
), 1.47 (9H, s, C(CH
3)
3
), 3.74 (1H, dd, JH-H = 12.0 Hz, JH-H
.0 Hz, CHa/b-6), 4.00 (1H, dd, JH-H = 12.0 Hz, JH-H = 6.0 Hz, CHa/b-6), 4.06–4.22 (4H, m, 2 × OCH
.40–4.56 (2H, m, CH-1, CH-5), 5.46 (0.5H, d, JH-H = 6.0 Hz, NH-3 or NH-7), 5.48 (0.5H, d, JH-H = 9.0
Hz, NH-3 or NH-7), 7.01 (0.5H, m, NH-3 or NH-7), 7.09 (0.5H, m, NH-3 or NH-7); C NMR (75 MHz,
=
),
2
3
2CH
3
3
3
1
3
3
3
CDCl
3
) δ
C
15.6 (CH
3
-2), 15.7 (CH
3
-2), 16.3 (d, JC-P = 1.5 Hz, OCH
2
CH
3
), 16.4 (d, JC-P = 2.3 Hz,
3
3
OCH
2CH
3), 16.4 (d, JC-P = 1.5 Hz, OCH
2
CH
3
), 16.4 (d, JC-P = 2.3 Hz, OCH
C-P = 157.5 Hz, CH-1), 41.3 (d, JC-P = 157.5 Hz, CH-1), 55.2 (CH
2
CH
3
), 28.2 (C(CH
3)
3), 41.2 (d,
1
1
2
J
2
-6), 55.3 (CH-5), 62.6 (d, JC-P = 6.8 Hz,
2
2
2
OCH
OCH
2
(
2CH
3), 62.6 (d, JC-P = 6.8 Hz, OCH
2CH
3
), 63.0 (d, JC-P = 6.8 Hz, OCH
2
CH
3
), 63.0 (d, JC-P = 6.8 Hz,
3
1
1
2CH
3), 80.8 (C(CH
3)
3
), 155.0 (C=O-8), 168.3 (C=O-4); P- Hdecoup NMR (121 MHz, CDCl
3
) δ
P), MH : 409.1266 ( Cl), 411.1237 ( Cl), found 409.1258
Cl), 411.1231 ( Cl). LCMS purity >95% (C-18 reversed phase, MeOH-H O).
P
24.7,
+
35
37
4.8; HRMS (NSI) calcd for (C14
H28ClN
2O6
35
37
2
(
R)-2-((S)-2-((tert-Butoxycarbonyl)amino)pentanamido)-3-chloropropanoic acid or Boc-L-Nva-β-chloro-L-
Ala-OH (23a). Deprotection of benzyl ester was followed, using (R)-benzyl 2-((S)-2-((tert-
butoxycarbonyl)amino)pentanamido)-3-chloropropanoate (22a) (5.8 mmol, 2.41 g) to afford 23a as a
light yellow solid (1.81 g, 5.61 mmol, 96%); m.p. 60–63 °C; ῡmax/cm 3312 (br OH), 2963 (NH), 1655
(
−
1
1
3
br C=O), 1509 (NH bend), 1161 (C-O); H NMR (300 MHz, DMSO) δ
H
0.85 (3H, t, JH-H = 9.0 Hz, CH
3-
7
’’), 1.24–1.34 (2H, m, CH
2
-7’), 1.38 (9H. s, C(CH
3
)
3
), 1.42–1.52 (1H, m, CHa/b-7), 1.54–1.59 (1H, m,
2
3
2
CHa/b-7), 3.34 (1H, br, OH), 3.84 (1H, dd, JH-H = 12.0 Hz, JH-H = 6.0 Hz, CHa/b-3), 3.91 (1H, dd, JH-H
=
=
2.0 Hz, 3JH-H = 6.0 Hz, CHa/b-3), 3.95–4.02 (1H, m, CH-6), 4.62–4.67 (1H, m, CH-2), 6.92 (1H, d, JH-H
3
1
9
3
13
.0 Hz, NH-8), 8.07 (1H, d, JH-H = 9.0 Hz, NH-4); C NMR (75 MHz, CDCl
-7’), 28.6 (C(CH ), 34.4 (CH -7), 45.1 (CH -3), 53.6 (CH-2), 54.5 (CH-6), 78.5 (C(CH
C=O-9), 170.6 (C=O-5), 173.0 (C=O-1); m/z (ESI) calcd for (C13
3) δ
C
14.1 (CH3-7’’), 19.1
(
CH
2
3)
3
2
2
3)
3), 155.8
+
5
+
35
(
H23ClN
2NaO
) , MNa : 345.1 ( Cl), 347.1