Table 2.

13C NMR data of premithramycins A1 to A4 at 125.7 MHz in d6-acetonea

C-1NOb 195.5 sc 196.2 sc 202.4 s
C-2113.1 s113.3 s113.2 s75.9 dc
C-3NOb 189.5 sc 189.0 sc 41.9 d
C-478.5 d78.3 d78.0 d26.4 t
C-4a43.0 d43.1 d43.0 d135.3 s
4-OCH3 61.1 q61.1 q61.4 q
C-526.6 t26.6 t26.6 t101.0 d
C-5a136.2 s134.8 s134.6 s
C-6117.9 d117.9 d117.8 d160.0 s
C-6a142.8 s140.3 s140.1 s
C-7103.2 d102.8 d102.8 d109.0 s
7-CH3 6.8 q
C-8160.8 sc 162.2 s162.1 s155.8 s
C-8a105.9 s
C-9102.2 d110.8 s110.7 sNOb
C-9a106.9 s
9-CH3 8.2 q8.2 q
C-10163.3 sc 157.7 s157.5 s115.2 d
C-10a107.8 s107.3 s107.1 s138.5 s
C-11168.0 s168.1 s168.0 s
C-11a108.3 s108.3 s108.0 s
C-12NOb 193.1 sc 193.0 sc
C-12a85.5 s85.5 s85.5 s
C-1′204.1 s204.3 s204.3 s81.0 dd
1′-OCH3 57.7 q
C-2′28.2 q28.4 q28.4 q210.3 s
C-3′78.1 de
C-4′67.4 de
C-5′18.7 q
C-1A98.2 d98.3 d98.3 dd 100.0 d
C-2A40.5 t38.6 t38.5 t37.0 t
C-3A71.9 d82.0 d81.9 d80.9 dd
C-4A77.9 d75.7 d75.6 d74.4 d
C-5A72.9 d72.9 d72.8 d71.6 d
C-6A18.2 q18.4 q18.5 q17.1 q
C-1B100.7 d100.5 d99.4 d
C-2B35.6 t32.8 t31.6 t
C-3B69.3 d77.1 d75.9 d
C-4B70.6 d69.2 d67.9 d
C-5B71.7 d71.2 d70.0 df
C-6B16.9 q16.9 q15.6 q
C-1C98.2 dd 97.0 d
C-2C44.6 t43.4 t
C-3C71.1 s69.7 s
3C-CH3 27.7 q26.1 q
C-4C77.1 d75.8 dc
C-5C71.3 d70.1 df
C-6C18.7 q17.4 q
  • a δ in parts per million relative to internal trimethylsilyl. Multiplicities and assignments are from the APT, hetero-multiple quantum correlation, and HMBC experiments.

  • b NO, not observed due to tautomerization.

  • c to f Assignments are interchangeable pairwise.