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. Author manuscript; available in PMC: 2008 Aug 15.
Published in final edited form as: J Med Chem. 2006 Jul 13;49(14):4344–4355. doi: 10.1021/jm060016l

Table 1.

Selected 13C and 1H NMR chemical shifts (ppm) for various α-amino acid esters of CPT and DB-67 and their corresponding hemiorthoesters (I′).

graphic file with name nihms-61190-t0002.jpg
 
  
  
  
  
  
  
 NMR assignment
  
  
Cmpd R1 R2 R3 R4 C-17 C-20 C-22 C-23 H-17 H-23 OHa
1 H H H H 66.3 77.4 167.0 50.2 5.56 (s) 4.08−4.39 (AB)
I′-1 - H H H 57.4 81.9 107.4 47.8 4.85−5.05 (AB) 3.33−3.49 (ABX) 7.93
2 H CH3 H H 66.4 77.7 166.8 47.9 5.56 (s) 4.30−4.47 (AB)
I′-2 - CH3 H H 57.4 82.0 107.1 54.8 4.83−5.06 (AB) 3.41−3.72 (AB) 8.06
3 CH3 CH3 H H 66.4 78.0 - 50.3 5.57 (s) 4.53−4.63 (AB)
4 H COCH3 H H 67.0 77.4 167.2 41.5 5.40−5.70 (AB) 4.15−4.45 (ABX)
5 H H TBS OH 66.3 77.5 166.8 52.2 5.52 (s) 4.10−4.31 (AB)
I′-5 - H TBS OH - - - - 4.73−5.12 (AB) 3.28−3.48 (ABX) 7.88
6 H CH3 TBS OH 67.8 80.0 - 54.3 5.48−5.63 (AB) 4.30−4.38 (AB)
I′-6 - CH3 TBS OH 57.3 82.0 107.0 52.0 4.73−5.11 (AB) 3.41−3.69 (AB) 7.96
a

22-Ortho hydroxyl group of I′