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Measurements and interpretations of NMR spectra

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					      Uppsala University
      Department of Chemistry
      Organic Chemistry

         NMR-Spectroscopy NV1
               Project

Measurements and interpretations of
         NMR spectra

           Joan Bertrand
             Alar Ainla

                  2005
Compound 1

• We knew formula C5H8O2
• So DBE=2
    Recorded spectra (300MHz)

•   Proton (H) spectrum
•   Carbon (C) spectrum
•   COSY
•   HSQC
•   HMBC
C spectrum




C=O
             C-O
H spectrum



             1.4ppm, integraal 3, doublet
                 Methyl, next to CH
          COSY




                           Eliminate
                          alternatives


                      X


                          X


High shift, next to
   O probably
COSY




       X
           X


               Left! COO
Initially concluded structure



             2       3
         1               4
     O                       5
                 O
HSQC (verify idea)




                         2       3
                     1               4
                 O                       5
                             O
HMBC




               2       3
           1               4
       O                       5
                   O
Compound 1
Compound 2

• Expected structure (Chinchonidin)
        15
        CH2

   14
                  16
      13

   12       17            N
                 18
                      10
        11
                      9       OH
        5        4
            4a
  6                       3

  7                       2
          8a N
        8
             1
    Recorded spectra (300MHz)

•   Proton (H) spectrum
•   Carbon (C) spectrum
•   COSY
•   HSQC
•   HMBC
•   NOESY
Proton spectrum
Carbon spectrum
HMBC and starting point
        15
        CH2

   14
                  16
      13

   12                     N
            17
                 18                Aliphatic protons and carbons
                      10
        11
                      9       OH
        5        4
            4a
  6                       3

  7                       2
            8a N
        8
               1


  Aromatic protons
  Aromatic and olefinic carbons

                                                  Cross-peak
                                                  Aromatic proton
                                                  Aliphatic carbon
HSQC  C-3, H-9
HMBC  C-10 or C-11

        15
        CH2

   14
                  16
      13

   12       17            N
                 18
                      10
        11
                      9       OH
        5        4
            4a
  6                       3

  7                       2
            8a N
        8
               1
HSQC  C-10, C-11, H-10/11
COSY  H-10, H-11 (verify)
HMBC – Next starting point




              Olefinic carbon connected
                 to aliphatic protons


                         15
                         CH2

                    14
                                   16
                        13

                    12       17            N
                                  18
                                       10
                         11
                                       9       OH
                         5        4
                             4a
                    6                      3

                    7                      2
                             8a N
                         8
                                1
HSQC  H-14
COSY  2 H-15 and H-13




                              15
                              CH2

                         14
                                        16
                             13

                         12       17            N
                                       18
                                            10
                              11
                                            9       OH
                              5        4
                                  4a
                         6                      3

                         7                      2
                                  8a N
                              8
                                     1
HSQCC-15, C-13, C/H-12, C/H-16




                                                            Vicinity. CH, CH2 peaks
                                                             Two carbon peaks in
                                 15
                                 CH2

                            14
                                           16
                                13
     Why we dont have any                          N
                            12       17
     other alternative?                   18
                                               10
                                 11
                                               9       OH
                                 5        4
                                     4a
                            6                      3

                            7                      2
                                     8a N
                                 8
                                        1
HMBC  C-18 and C-17


                                   H-11, H-12 C-17




        15
        CH2

   14
                  16
      13

   12       17            N
                 18
                      10
        11
                      9       OH
        5        4
            4a
  6                       3

  7                       2
            8a N
        8
               1
HSQC H 17 and 18
Aliphatic region assigned


     Aromatic ????
COSY H-2


           15
           CH2

      14
                     16
          13

      12       17            N
                    18
                         10
           11
                         9       OH
           5        4
               4a
      6                      3

      7                      2
               8a N
           8
                  1
HMBC  Looking for a next step




              Singlet. 3H
                                           15
                                           CH2
   High shift, similar to –O-Met      14
                                                     16
                                          13

                                      12       17            N
                                                    18
                   Missing proton??                      10
                                           11
                                                         9       OH
                                           5        4
                                               4a
                                      6                      3

                                      7                      2
                                               8a N
                                           8
                                                  1
Structure
                     15
                     CH2

                14
                               16
                    13

                12       17            N
                              18
                                   10
                     11
                                   9       OH
     CH3    O        5        4
                         4a
                6                      3

                7                      2
                       8a N
                     8
                          1
HMBC  C-Met, C-6




                        Met

                7 6 O               H
                               12       14
            8          5    11               15
           8a         4a H     17       13
            N              H
                                 18
                      4 9 10            16
                2   3              N
                         OH
NOESY  H-8, H-7, H-5


                 Met

         7 6 O               H
                        12       14
     8          5    11               15
    8a         4a H     17       13
     N              H
                          18
               4 9 10            16
         2   3              N
                  OH




                                           Shift!
HSQC  C-8, (C-7/5)
HMBC  C-7 and C-5




                            Met

                    7 6 O               H
                                   12       14
                8          5    11               15
               8a         4a H     17       13
                N              H
                                     18
                          4 9 10            16
                    2   3              N
                             OH
HMBC  unprotonated carbons
C-4, C-4a, C-8a



           C-8a

            C-4a, J3 more sensitive

           C-8a
                          Met
             C-4a, J3 more sensitive
                  7 6 O                 H
                                    12      14
                8        5    11                 15
               8a       4a H       17       13
                 N           H
                                     18
                        4 9 10              16
                  2
           Thus C-4 3                  N
                           OH
All signals assigned!
Stereochemistry NOESY


         H-16 pointing downwards




                                                     H-17 pointing toward H-13
                                                      H-11 pointing upwards
                           Met

                   7 6 O               H
                                  12       14
               8          5    11               15
              8a         4a H     17       13
               N              H
                                    18
                         4 9 10            16
                   2   3              N
                            OH
Finally everything is assigned 
Conclusion

• This project was …
  – A lot of interesting challenge
  – A lot of mind boggling thoughts
  – A lot of pleasure when the puzzle
    became finally solved


                  
"If we knew what it was we were
doing, it would not be called
   research, would it?"
        THANK YOU!
              - Albert Einstein

				
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posted:8/10/2012
language:English
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