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Using 2D NMR
Strategy
Organic Structure Analysis, Crews, Rodriguez and Jaspars
Organic Structure Analysis, Crews, Rodriguez and Jaspars
Molecularformula
Functionalgroups
Substructures
Very secure3D molecular
structure
MS, NMR
NMR, IR
UV
NMR
X-RAY
UnsaturationNumber(UN)
Working 2D
structures
List of working
2D structures
Reasonable3D molecular
structure
New 2Dmolecularstructure
NMR
ORD Totalsynthesis Molecular
modeling
Knownmolecularstructure
Dereplicate by MF
Dereplicate
Draw all isomers
NMR, MS, IR, UV
by structure
Purecompound
THE PROCESS OF STRUCTURE ELUCIDATION
Organic Structure Analysis, Crews, Rodriguez and Jaspars
C10H18OUnknownAnalysis
Determine molecularformula
OH
H
IR/1H NMR/Tests
Determinefunctionalgroups
OH
H
1H NMR/IR
Assemble completelist of substructures
All substructures add up to molecular formula
3
OH OH Combine substructuresin all possible ways
Three possible structureswith correct MF and dbe(There are many more)
OH
OH
Use NMR evidence torule out or confirmstructures
Chosen structureconfirm using data tables
Organic Structure Analysis, Crews, Rodriguez and Jaspars
13C spectrum/DEPT-135
Low Resolution MS
m/z 335 [M+H]+
APT Formula C20H29
High Resolution MS
m/z 335.2222 [M+H]+
Molecular Formula C20H30O4
Crystal Unit Cell Dimensions
DATABASE
Substructures
1D NMR Spectra 2D NMR Spectra
DEREPLICATION:The process of rapidlydiscovering whethera compound haspreviously been reported.
Organic Structure Analysis, Crews, Rodriguez and Jaspars
Get 13C NMR spectrum
get multiplicities
STRATEGY BASED ON C-C CONNECTIVITY
Get 2D INADEQUATE Make C-C map
Get 13C-1H correlation spectrum
(HSQC)
Get one bond 13C-1H correlations
assign 1H resonances
Bridge heteroatoms
using long range 13C-1H correlation spectrum
(eg HMBC) or using nOe data
Generate 2D structure
• Based on 13C-13C correlations – 1/10 000 chance• Need large amounts of sample• Sample must have high solubility• Need long acquisition times (>24 h)• Correlations across heteroatoms not possible – these must be
determined using HMBC data• Gives no information about C-H correlations – need to get
HSQC data to assign protons• BUT: If possible to use INADEQUATE, connectivity information
is unambiguous (unlike HMBC)
STRATEGY BASED ON C-C CONNECTIVITY PROBLEMS
Organic Structure Analysis, Crews, Rodriguez and Jaspars
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-C CONNECTIVITYEXAMPLE13C axis
(ppm)
Double quantum axis (Hz)
A
B
C
D
E
F
A-B
A-D
D-C
C-EF-B
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-C CONNECTIVITYEXAMPLE
F B A D C E
Gives topology of molecule
Chemical shift information gives:
F
B
A
D
C
E
OH
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-C CONNECTIVITYREAL EXAMPLE
A-B
A-I
A-K
D-CB-E
B-F E-C
D-GF-D
D-JC-N
G-H
E-ME-L
I-JH-N
G-O
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-C CONNECTIVITYREAL EXAMPLE
Data: A-B, A-I, A-K, B-E, B-F, E-C, E-L, E-M, C-D, C-N, N-H, H-G, G-D, G-O, D-F, D-J, J-I
A
K
B
I
F
E
ML
C
D
NH
G
O JOH
CEDROL
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY
H
C C
HHSQCHSQC &
H
C C
H
1H-1H COSY
C C
H
C C C
HSQC &H
C C C
HMBC
C C C
HMBC data is ambiguous (2 or 3 bond correlations – impossible to tell which)
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY
Get 1H, 13C NMR spectra
get multiplicities and integrals
Get one bond 13C-1H correlations
assign 1H resonances to 13C resonancesGet 1H-1H correlation data (eg COSY)
Check assignment of diastereotopic protonsusing COSY and HMQC
Assemble substructures using COSY data
Get long range 13C-1H correlation spectrum
(eg HMBC)Combine substructures into
all possible working structures
Check all working structures for consistencywith 2D NMR data
2D structure
Get 13C-1H correlation spectrum (eg HSQC)
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – DEPT DATA
CCH2
CH, CH3
CHCH CH
CH2
CH3 CH3
ABC
D(C)0 + (CH)3 + (CH2)1 + (CH3)2 = C6H11 = 83
EF
LRMS = 100 m/z so add OH MF = C6H12O
C
Label from leftto right in capitals
A B C D E F
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – HSQC DATA
A B C D E F C
ab
c
d’d
ef
label protons in lower case letters
diastereotopicprotons
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – HSQC DATA
ATOM C (ppm) DEPT H (ppm)
A 131 CH 5.5
B 124 CH 5.2
C 68 CH 4.0
D 42 CH2 3.0
2.5
E 23 CH3 1.5
F 17 CH3 1.2
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – HSQC DATA
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – HSQC DATA
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – HSQC DATA
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – HSQC DATA
diastereotopic protons
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – COSY DATA
ab
c
d
d'
ef
a b c d d' e f
Vicinal (3 bond)
Geminal (2 bond)
4 bondDiagonal
a-b
a-d/d’
b-fc-e
And many more…
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – COSY DATA
ATOM C (ppm) DEPT H (ppm) COSY (HH)
A 131 CH 5.5 b, c, d/d’, f
B 124 CH 5.2 a, d/d’, f
C 68 CH 4.0 a, d/d’, e
D 42 CH2 3.0
2.5
a, b, c, d, e
E 23 CH3 1.5 c, d/d’
F 17 CH3 1.2 a, b
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – COSY DATA
diagonal
r
r
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – COSY DATA
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – COSY DATAHSQC suggests diastereotopic protons:3.08/2.44 ppm1.86/2.07 ppm
OK?
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – HMBC DATA
A B C D E F
ab
c
d
d'
ef
C
H
B-a C-a
A-b
D-c
And many more…
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – HMBC DATA
ATOM C (ppm) DEPT H (ppm) COSY (HH) HMBC (CH)
A 131 CH 5.5 b, c, d/d’, f b, c, d, f
B 124 CH 5.2 a, d/d’, f a, d, f
C 68 CH 4.0 a, d/d’, e a, d, e
D 42 CH2 3.0
2.5
a, b, c, d, e a, b, c, e
E 23 CH3 1.5 c, d/d’ c, d
F 17 CH3 1.2 a, b a, b
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – HMBC DATA
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – HMBC DATA
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITY – HMBC DATA
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITYRETROSPECTIVE CHECKING
Pieces:
A
H
B
H
C
OH
H
D
HH
E
H H
H
F
H H
H
C 131 C 124 C 68 C 42 C 23 C 17
H 5.5 H 5.2H 4.0
H 3.0H 2.5
H 1.5 H 1.2
Possibilities:
F
A
B
C
D
E
OH
F
B
A
C
D
E
OH
E
B
A
C
D
F
OH
E
A
B
C
D
F
OH
F
D
A
B
C
E
OH
E
D
B
A
C
E
OH
E
D
A
B
C
E
OH
F
D
B
A
C
E
OH
F
A
B
D
C
E
OH
E
B
A
D
C
F
OH
E
A
B
D
C
F
OH
F
B
A
D
C
E
OH
Combinatorialexplosion
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITYRETROSPECTIVE CHECKING
MeF
B
A
D
C
MeE
OH
Hb
Ha
Hd Hd'
Hc
HMBC data (C-C-H & C-C-C-H) from C H
And similarly for COSY data
Organic Structure Analysis, Crews, Rodriguez and Jaspars
PROSPECTIVE CHECKING
Pieces: A
H
B
H
C
OH
H
D
HH
E
H H
H
F
H H
H
C 131 C 124 C 68 C 42 C 23 C 17
H 5.5 H 5.2H 4.0
H 3.0H 2.5
H 1.5 H 1.2
A B
Reason: only 2 sp2 C's
A B
F
HMBC: F-a, F-b, A-f, B-f
A B
F
DHMBC: D-a, D-b, A-d, B-d
A B
F
DC
OH
HMBC: C-d, C-a, D-c, A-cA B
F
DC
E
OH
HMBC: E-c, E-d, C-e, C-d
Organic Structure Analysis, Crews, Rodriguez and Jaspars
COMPARISON OF C-H AND C-C STRATEGIES
C-C Strategy C-H Strategy
Experiment Time Experiment Time1H NMR < 1 min 1H NMR 1 min13C NMR < 1 min 13C NMR 1 – 4 h
DEPT 135 < 1 min DEPT 135 1 – 4 h
HSQC nt=1, ni=256 15 min HSQC nt=4, ni=256 1 h
HMBC nt=1, ni=512 15 min HMBC nt=4, ni=512 1 h
NOESY nt=4, ni=256 1 h NOESY nt=4, ni=256 1 h
INADEQUATE 24 h COSY nt=1, ni=256 15 min
Total time ~26 h 6 – 12 h
Sample conc 6 M 10 – 100 mM
Organic Structure Analysis, Crews, Rodriguez and Jaspars
EXERCISE 1. For a simple organic compound the mass spectrum shows a molecular ion at m/z 98. The following data has been obtained from various 1D and 2D NMR experiments. Using this information determine the structure of the molecule in question and rationalise the 2D NMR data given.
Atom dC (ppm) dH (ppm) 1H - 1H COSY
(3 bond only)
1H 13C Long range
(2 - 3 bonds)
A 218 s - - A-b, A-c, A-d, A-e
B 47 t 1.8 dd b-d B-c, B-d, B-e, B-f
C 38 t 2.3 m c-e C-b, C-d, C-e
D 32 d 1.5 m d-b, d-e, d-f D-b, D-c, D-e, D-f
E 31 t 2.2 m e-c, e-d E-b, E-c, E-d, E-f
F 20 q 1.1 d f-d F-b, F-d, F-e
Organic Structure Analysis, Crews, Rodriguez and Jaspars
EXERCISE 2. For a simple organic compound the mass spectrum shows a molecular ion at m/z 114. The following data has been obtained from various 1D and 2D NMR experiments. Using this information determine the structure of the molecule in question and rationalise the 2D NMR data given.
An additional peak is present in the 1H NMR at 11.6 ppm (bs).
Atom dC (ppm) dH (ppm) 1H - 1H COSY
(3 bond only)
1H 13C Long range
(2 - 3 bonds)
A 178 s - - A-d, A-b
B 136 d 5.7 m b-c, b-d B-d, B-c, B-e
C 118 d 5.5 m c-b, c-e C-b, C-d, C-e, C-f
D 38 t 3.0 d d-b D-b, D-c
E 25 t 2.1 m e-c, e-f E-b, E-c, E-f
F 13 q 1.0 t f-e F-c, F-e
Organic Structure Analysis, Crews, Rodriguez and Jaspars
SELECTIVE 1D - TOCSY
Spin-lock90o
(selective)
Preparation DetectionMixing
J. Mag. Res. 1989, 85, 1-14. J. Mag. Res. 1989, 81, 186-190
Organic Structure Analysis, Crews, Rodriguez and Jaspars
SELECTIVE 1D – TOCSYSUBSPECTRA
8 7 6 5 4 3 2 1 ppm
NNH
N
O
ON S
O
OMe
8 7 6 5 4 3 2 1 ppm
Organic Structure Analysis, Crews, Rodriguez and Jaspars
OOH
HOH
HHO
H
H
Mystery Compound:
Eunicellin
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-C CONNECTIVITYREAL EXAMPLE
Data: A-B, A-I, A-K, B-E, B-F, E-C, E-L, E-M, C-D, C-N, N-H, H-G, G-D, G-O, D-F, D-J, J-I
Organic Structure Analysis, Crews, Rodriguez and Jaspars
STRATEGY BASED ON C-H CONNECTIVITYRETROSPECTIVE CHECKING
Pieces:
A
H
B
H
C
OH
H
D
HH
E
H H
H
F
H H
H
C 131 C 124 C 68 C 42 C 23 C 17
H 5.5 H 5.2H 4.0
H 3.0H 2.5
H 1.5 H 1.2
Possibilities:
F
A
B
C
D
E
OH
F
B
A
C
D
E
OH
E
B
A
C
D
F
OH
E
A
B
C
D
F
OH
F
D
A
B
C
E
OH
E
D
B
A
C
E
OH
E
D
A
B
C
E
OH
F
D
B
A
C
E
OH
F
A
B
D
C
E
OH
E
B
A
D
C
F
OH
E
A
B
D
C
F
OH
F
B
A
D
C
E
OH