NP-MRD: Showing NP-Card for {6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid (NP0292919)

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Record Information

Version

2.0

Created at

2022-09-10 00:40:31 UTC

Updated at

2022-09-10 00:40:31 UTC

NP-MRD ID

NP0292919

Secondary Accession Numbers

None

Natural Product Identification

Common Name

{6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid

Description

Sulfocostunolide A belongs to the class of organic compounds known as guaianolides and derivatives. These are diterpene lactones with a structure characterized by the presence of a gamma-lactone fused to a guaiane, forming 3,6,9-trimethyl-azuleno[4,5-b]furan-2-one or a derivative. {6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid is found in Saussurea costus. Sulfocostunolide A is an extremely weak basic (essentially neutral) compound (based on its pKa).

Structure

MOL 3D MOL SDF PDB SMILES InChI

     RDKit          3D

 41 43  0  0  0  0  0  0  0  0999 V2000
   -1.5728   -2.8142    0.7825 C   0  0  0  0  0  0  0  0  0  0  0  0
   -1.2751   -1.8898   -0.1137 C   0  0  0  0  0  0  0  0  0  0  0  0
   -0.0611   -2.0934   -0.9403 C   0  0  0  0  0  0  0  0  0  0  0  0
    1.1404   -1.3840   -0.4060 C   0  0  0  0  0  0  0  0  0  0  0  0
    0.9706    0.0673   -0.1606 C   0  0  1  0  0  0  0  0  0  0  0  0
    2.0662    0.8213   -0.8322 C   0  0  2  0  0  0  0  0  0  0  0  0
    3.1172    1.3683    0.0616 C   0  0  0  0  0  0  0  0  0  0  0  0
    3.9981    0.1944    1.0135 S   0  0  0  0  0  6  0  0  0  0  0  0
    5.0907    0.9583    1.7559 O   0  0  0  0  0  0  0  0  0  0  0  0
    3.1683   -0.4518    2.0865 O   0  0  0  0  0  0  0  0  0  0  0  0
    4.8043   -0.9350    0.0658 O   0  0  0  0  0  0  0  0  0  0  0  0
    1.3761    1.9951   -1.4603 C   0  0  0  0  0  0  0  0  0  0  0  0
    1.8952    2.8940   -2.1651 O   0  0  0  0  0  0  0  0  0  0  0  0
    0.0258    1.9472   -1.1401 O   0  0  0  0  0  0  0  0  0  0  0  0
   -0.3037    0.6447   -0.7696 C   0  0  2  0  0  0  0  0  0  0  0  0
   -1.3877    0.4886    0.2265 C   0  0  1  0  0  0  0  0  0  0  0  0
   -2.4515    1.4875    0.2517 C   0  0  0  0  0  0  0  0  0  0  0  0
   -2.4349    2.7907    0.0182 C   0  0  0  0  0  0  0  0  0  0  0  0
   -3.7195    0.7547    0.6283 C   0  0  0  0  0  0  0  0  0  0  0  0
   -3.2816   -0.7057    0.8082 C   0  0  0  0  0  0  0  0  0  0  0  0
   -2.1776   -0.7588   -0.1999 C   0  0  2  0  0  0  0  0  0  0  0  0
   -0.9061   -3.6812    0.8663 H   0  0  0  0  0  0  0  0  0  0  0  0
   -2.4132   -2.8020    1.4446 H   0  0  0  0  0  0  0  0  0  0  0  0
    0.1886   -3.1950   -0.9104 H   0  0  0  0  0  0  0  0  0  0  0  0
   -0.2114   -1.8788   -2.0133 H   0  0  0  0  0  0  0  0  0  0  0  0
    1.9743   -1.5769   -1.1366 H   0  0  0  0  0  0  0  0  0  0  0  0
    1.4007   -1.8986    0.5657 H   0  0  0  0  0  0  0  0  0  0  0  0
    0.9848    0.3317    0.9201 H   0  0  0  0  0  0  0  0  0  0  0  0
    2.4853    0.2400   -1.6991 H   0  0  0  0  0  0  0  0  0  0  0  0
    2.6444    2.0891    0.7552 H   0  0  0  0  0  0  0  0  0  0  0  0
    3.8420    1.9274   -0.5574 H   0  0  0  0  0  0  0  0  0  0  0  0
    5.6232   -1.2790    0.4927 H   0  0  0  0  0  0  0  0  0  0  0  0
   -0.5437    0.1067   -1.7336 H   0  0  0  0  0  0  0  0  0  0  0  0
   -0.9679    0.3425    1.2472 H   0  0  0  0  0  0  0  0  0  0  0  0
   -3.3692    3.3342    0.1038 H   0  0  0  0  0  0  0  0  0  0  0  0
   -1.5378    3.3559   -0.2524 H   0  0  0  0  0  0  0  0  0  0  0  0
   -4.0454    1.1755    1.5811 H   0  0  0  0  0  0  0  0  0  0  0  0
   -4.4715    0.8327   -0.1853 H   0  0  0  0  0  0  0  0  0  0  0  0
   -4.1045   -1.3606    0.4684 H   0  0  0  0  0  0  0  0  0  0  0  0
   -2.9679   -0.8951    1.8469 H   0  0  0  0  0  0  0  0  0  0  0  0
   -2.5918   -0.5480   -1.1880 H   0  0  0  0  0  0  0  0  0  0  0  0
 11  8  1  0
  8  9  2  0
  8 10  2  0
  8  7  1  0
  7  6  1  0
  6  5  1  0
  5  4  1  0
  4  3  1  0
  3  2  1  0
  2  1  2  3
  2 21  1  0
 21 20  1  0
 20 19  1  0
 19 17  1  0
 17 18  2  3
 17 16  1  0
 16 15  1  0
 15 14  1  0
 14 12  1  0
 12 13  2  0
 12  6  1  0
 15  5  1  0
 16 21  1  0
 11 32  1  0
  7 30  1  0
  7 31  1  0
  6 29  1  6
  5 28  1  1
  4 26  1  0
  4 27  1  0
  3 24  1  0
  3 25  1  0
  1 22  1  0
  1 23  1  0
 21 41  1  6
 20 39  1  0
 20 40  1  0
 19 37  1  0
 19 38  1  0
 18 35  1  0
 18 36  1  0
 16 34  1  1
 15 33  1  6
M  END


  Mrv1533004161516382D          

 21 23  0  0  0  0            999 V2000
   -1.5764   -0.8731    0.0000 O   0  0  0  0  0  0  0  0  0  0  0  0
   -0.8386   -0.5040    0.0000 S   0  0  0  0  0  0  0  0  0  0  0  0
   -0.4695   -1.2419    0.0000 O   0  0  0  0  0  0  0  0  0  0  0  0
   -1.2076    0.2338    0.0000 O   0  0  0  0  0  0  0  0  0  0  0  0
   -0.1007   -0.1350    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    0.5878   -0.5895    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    1.3602   -0.2996    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    1.5438    0.5047    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    2.2871    0.8627    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    3.0304    0.5047    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    3.6754    1.0191    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    3.2140   -0.2996    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    3.9864   -0.5895    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    3.9493   -1.4137    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    3.1541   -1.6331    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    2.8642   -2.4055    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    2.6996   -0.9446    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    1.8746   -0.9446    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    1.4201   -1.6331    0.0000 O   0  0  0  0  0  0  0  0  0  0  0  0
    0.6248   -1.4137    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
   -0.0202   -1.9280    0.0000 O   0  0  0  0  0  0  0  0  0  0  0  0
  1  2  1  0  0  0  0
  2  3  2  0  0  0  0
  2  4  2  0  0  0  0
  2  5  1  0  0  0  0
  5  6  1  0  0  0  0
  6  7  1  0  0  0  0
  7  8  1  0  0  0  0
  8  9  1  0  0  0  0
  9 10  1  0  0  0  0
 10 11  2  0  0  0  0
 10 12  1  0  0  0  0
 12 13  1  0  0  0  0
 13 14  1  0  0  0  0
 14 15  1  0  0  0  0
 15 16  2  0  0  0  0
 15 17  1  0  0  0  0
 12 17  1  0  0  0  0
 17 18  1  0  0  0  0
  7 18  1  0  0  0  0
 18 19  1  0  0  0  0
 19 20  1  0  0  0  0
  6 20  1  0  0  0  0
 20 21  2  0  0  0  0
M  END
> <DATABASE_ID>
NP0292919

> <DATABASE_NAME>
NP-MRD

> <SMILES>
OS(=O)(=O)CC1C2CCC(=C)C3CCC(=C)C3C2OC1=O

> <INCHI_IDENTIFIER>
InChI=1S/C15H20O5S/c1-8-3-6-11-12(7-21(17,18)19)15(16)20-14(11)13-9(2)4-5-10(8)13/h10-14H,1-7H2,(H,17,18,19)

> <INCHI_KEY>
IDSMFDGIKYVJPL-UHFFFAOYSA-N

> <FORMULA>
C15H20O5S

> <MOLECULAR_WEIGHT>
312.38

> <EXACT_MASS>
312.103144918

> <JCHEM_ACCEPTOR_COUNT>
4

> <JCHEM_ATOM_COUNT>
41

> <JCHEM_AVERAGE_POLARIZABILITY>
31.49238088012153

> <JCHEM_BIOAVAILABILITY>
1

> <JCHEM_DONOR_COUNT>
1

> <JCHEM_FORMAL_CHARGE>
0

> <JCHEM_GHOSE_FILTER>
1

> <JCHEM_IUPAC>
{6,9-dimethylidene-2-oxo-dodecahydroazuleno[4,5-b]furan-3-yl}methanesulfonic acid

> <ALOGPS_LOGP>
-0.01

> <JCHEM_LOGP>
1.363222073666667

> <ALOGPS_LOGS>
-2.46

> <JCHEM_MDDR_LIKE_RULE>
0

> <JCHEM_NUMBER_OF_RINGS>
3

> <JCHEM_PHYSIOLOGICAL_CHARGE>
-1

> <JCHEM_PKA_STRONGEST_ACIDIC>
-0.7346528907938268

> <JCHEM_PKA_STRONGEST_BASIC>
-7.10148033120274

> <JCHEM_POLAR_SURFACE_AREA>
80.66999999999999

> <JCHEM_REFRACTIVITY>
76.33670000000001

> <JCHEM_ROTATABLE_BOND_COUNT>
2

> <JCHEM_RULE_OF_FIVE>
1

> <ALOGPS_SOLUBILITY>
1.09e+00 g/l

> <JCHEM_TRADITIONAL_IUPAC>
{6,9-dimethylidene-2-oxo-octahydro-3H-azuleno[4,5-b]furan-3-yl}methanesulfonic acid

> <JCHEM_VEBER_RULE>
0

$$$$

HEADER    PROTEIN                                 16-APR-15   NONE
TITLE     NULL                                                        
COMPND    NULL                                                        
SOURCE    NULL                                                        
KEYWDS    NULL                                                        
EXPDTA    NULL                                                        
AUTHOR    Marvin                                                      
REVDAT   1   16-APR-15         0                                  
HETATM    1  O   UNK     0      -2.943  -1.630   0.000  0.00  0.00           O+0
HETATM    2  S   UNK     0      -1.565  -0.941   0.000  0.00  0.00           S+0
HETATM    3  O   UNK     0      -0.876  -2.318   0.000  0.00  0.00           O+0
HETATM    4  O   UNK     0      -2.254   0.436   0.000  0.00  0.00           O+0
HETATM    5  C   UNK     0      -0.188  -0.252   0.000  0.00  0.00           C+0
HETATM    6  C   UNK     0       1.097  -1.100   0.000  0.00  0.00           C+0
HETATM    7  C   UNK     0       2.539  -0.559   0.000  0.00  0.00           C+0
HETATM    8  C   UNK     0       2.882   0.942   0.000  0.00  0.00           C+0
HETATM    9  C   UNK     0       4.269   1.610   0.000  0.00  0.00           C+0
HETATM   10  C   UNK     0       5.657   0.942   0.000  0.00  0.00           C+0
HETATM   11  C   UNK     0       6.861   1.902   0.000  0.00  0.00           C+0
HETATM   12  C   UNK     0       5.999  -0.559   0.000  0.00  0.00           C+0
HETATM   13  C   UNK     0       7.441  -1.100   0.000  0.00  0.00           C+0
HETATM   14  C   UNK     0       7.372  -2.639   0.000  0.00  0.00           C+0
HETATM   15  C   UNK     0       5.888  -3.049   0.000  0.00  0.00           C+0
HETATM   16  C   UNK     0       5.346  -4.490   0.000  0.00  0.00           C+0
HETATM   17  C   UNK     0       5.039  -1.763   0.000  0.00  0.00           C+0
HETATM   18  C   UNK     0       3.499  -1.763   0.000  0.00  0.00           C+0
HETATM   19  O   UNK     0       2.651  -3.049   0.000  0.00  0.00           O+0
HETATM   20  C   UNK     0       1.166  -2.639   0.000  0.00  0.00           C+0
HETATM   21  O   UNK     0      -0.038  -3.599   0.000  0.00  0.00           O+0
CONECT    1    2                                                            
CONECT    2    1    3    4    5                                             
CONECT    3    2                                                            
CONECT    4    2                                                            
CONECT    5    2    6                                                       
CONECT    6    5    7   20                                                  
CONECT    7    6    8   18                                                  
CONECT    8    7    9                                                       
CONECT    9    8   10                                                       
CONECT   10    9   11   12                                                  
CONECT   11   10                                                            
CONECT   12   10   13   17                                                  
CONECT   13   12   14                                                       
CONECT   14   13   15                                                       
CONECT   15   14   16   17                                                  
CONECT   16   15                                                            
CONECT   17   15   12   18                                                  
CONECT   18   17    7   19                                                  
CONECT   19   18   20                                                       
CONECT   20   19    6   21                                                  
CONECT   21   20                                                            
MASTER        0    0    0    0    0    0    0    0   21    0   46    0
END

View in JSmol

Synonyms

Value	Source
Sulphocostunolide a	Generator
Sulfocostunolide b	MeSH

Chemical Formula

C₁₅H₂₀O₅S

Average Mass

312.3800 Da

Monoisotopic Mass

312.10314 Da

IUPAC Name

{6,9-dimethylidene-2-oxo-dodecahydroazuleno[4,5-b]furan-3-yl}methanesulfonic acid

Traditional Name

{6,9-dimethylidene-2-oxo-octahydro-3H-azuleno[4,5-b]furan-3-yl}methanesulfonic acid

CAS Registry Number

Not Available

SMILES

OS(=O)(=O)CC1C2CCC(=C)C3CCC(=C)C3C2OC1=O

InChI Identifier

InChI=1S/C15H20O5S/c1-8-3-6-11-12(7-21(17,18)19)15(16)20-14(11)13-9(2)4-5-10(8)13/h10-14H,1-7H2,(H,17,18,19)

InChI Key

IDSMFDGIKYVJPL-UHFFFAOYSA-N

Experimental Spectra

Not Available

Predicted Spectra

Spectrum Type	Description	Depositor ID	Depositor Organization	Depositor	Deposition Date	View
1D NMR	¹³C NMR Spectrum (1D, 25 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹H NMR Spectrum (1D, 100 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹³C NMR Spectrum (1D, 252 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹H NMR Spectrum (1D, 1000 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹³C NMR Spectrum (1D, 50 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹H NMR Spectrum (1D, 200 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹³C NMR Spectrum (1D, 75 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹H NMR Spectrum (1D, 300 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹³C NMR Spectrum (1D, 101 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹H NMR Spectrum (1D, 400 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹³C NMR Spectrum (1D, 126 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹H NMR Spectrum (1D, 500 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹³C NMR Spectrum (1D, 151 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹H NMR Spectrum (1D, 600 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹³C NMR Spectrum (1D, 176 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹H NMR Spectrum (1D, 700 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹³C NMR Spectrum (1D, 201 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹H NMR Spectrum (1D, 800 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹³C NMR Spectrum (1D, 226 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum
1D NMR	¹H NMR Spectrum (1D, 900 MHz, H₂O, predicted)	Wishart Lab	Wishart Lab	David Wishart	2021-06-20	View Spectrum

Chemical Shift Submissions

Not Available

Species

Species of Origin

Species Name	Source	Reference
Saussurea costus	LOTUS Database	35616633

Chemical Taxonomy

Description

Belongs to the class of organic compounds known as guaianolides and derivatives. These are diterpene lactones with a structure characterized by the presence of a gamma-lactone fused to a guaiane, forming 3,6,9-trimethyl-azuleno[4,5-b]furan-2-one or a derivative.

Kingdom

Organic compounds

Super Class

Lipids and lipid-like molecules

Class

Prenol lipids

Sub Class

Terpene lactones

Direct Parent

Guaianolides and derivatives

Alternative Parents

Substituents

Guaianolide-skeleton
Guaiane sesquiterpenoid
Sesquiterpenoid
Gamma butyrolactone
Oxolane
Organic sulfonic acid or derivatives
Organosulfonic acid or derivatives
Organosulfonic acid
Sulfonyl
Alkanesulfonic acid
Lactone
Carboxylic acid ester
Oxacycle
Monocarboxylic acid or derivatives
Carboxylic acid derivative
Organoheterocyclic compound
Organosulfur compound
Organooxygen compound
Hydrocarbon derivative
Carbonyl group
Organic oxygen compound
Organic oxide
Aliphatic heteropolycyclic compound

Molecular Framework

Aliphatic heteropolycyclic compounds

External Descriptors

Not Available

Physical Properties

State

Not Available

Experimental Properties

Property	Value	Reference
Melting Point	Not Available	Not Available
Boiling Point	Not Available	Not Available
Water Solubility	Not Available	Not Available
LogP	Not Available	Not Available

Predicted Properties

Property	Value	Source
logP	-0.01	ALOGPS
logP	1.36	ChemAxon
logS	-2.5	ALOGPS
pKa (Strongest Acidic)	-0.73	ChemAxon
pKa (Strongest Basic)	-7.1	ChemAxon
Physiological Charge	-1	ChemAxon
Hydrogen Acceptor Count	4	ChemAxon
Hydrogen Donor Count	1	ChemAxon
Polar Surface Area	80.67 Å²	ChemAxon
Rotatable Bond Count	2	ChemAxon
Refractivity	76.34 m³·mol⁻¹	ChemAxon
Polarizability	31.49 Å³	ChemAxon
Number of Rings	3	ChemAxon
Bioavailability	Yes	ChemAxon
Rule of Five	Yes	ChemAxon
Ghose Filter	Yes	ChemAxon
Veber's Rule	No	ChemAxon
MDDR-like Rule	No	ChemAxon

External Links

HMDB ID

Not Available

DrugBank ID

Not Available

Phenol Explorer Compound ID

Not Available

FoodDB ID

Not Available

KNApSAcK ID

Not Available

Chemspider ID

Not Available

KEGG Compound ID

Not Available

BioCyc ID

Not Available

BiGG ID

Not Available

Wikipedia Link

Not Available

METLIN ID

Not Available

PubChem Compound

78062324

PDB ID

Not Available

ChEBI ID

Not Available

Good Scents ID

Not Available

References

General References

LOTUS database [Link]

Showing NP-Card for {6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid (NP0292919)

MOL for NP0292919 ({6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid)

3D MOL for NP0292919 ({6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid)

3D SDF for NP0292919 ({6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid)

3D-SDF for NP0292919 ({6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid)

PDB for NP0292919 ({6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid)

3D PDB for NP0292919 ({6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid)

SMILES for NP0292919 ({6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid)

INCHI for NP0292919 ({6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid)

Structure for NP0292919 ({6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid)

3D Structure for NP0292919 ({6,9-dimethylidene-2-oxo-octahydro-3h-azuleno[4,5-b]furan-3-yl}methanesulfonic acid)