NP-MRD: Showing NP-Card for 5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one (NP0322298)

Jump To Section:

Identification Spectra BioTaxonomy ChemoTaxonomy Physical properties Links References XML

Record Information

Version

2.0

Created at

2022-09-12 00:59:43 UTC

Updated at

2022-09-12 00:59:43 UTC

NP-MRD ID

NP0322298

Secondary Accession Numbers

None

Natural Product Identification

Common Name

5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one

Description

4-Epiisoinuviscolide 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. 4-Epiisoinuviscolide is an extremely weak basic (essentially neutral) compound (based on its pKa). Outside of the human body, 4-Epiisoinuviscolide has been detected, but not quantified in, herbs and spices. 5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one is found in Apalochlamys spectabilis, Carpesium abrotanoides, Carpesium faberi, Dittrichia graveolens, Helichrysum dasyanthum, Inula caspica, Inula helenium and Pentanema britannicum. This could make 4-epiisoinuviscolide a potential biomarker for the consumption of these foods.

Structure

MOL 3D MOL SDF PDB SMILES InChI

     RDKit          3D

 38 40  0  0  0  0  0  0  0  0999 V2000
    3.1239   -2.6550   -0.0908 C   0  0  0  0  0  0  0  0  0  0  0  0
    2.9149   -1.4026   -0.4329 C   0  0  0  0  0  0  0  0  0  0  0  0
    3.9490   -0.4920   -0.9156 C   0  0  0  0  0  0  0  0  0  0  0  0
    5.1685   -0.7426   -1.1752 O   0  0  0  0  0  0  0  0  0  0  0  0
    3.3712    0.7877   -1.0641 O   0  0  0  0  0  0  0  0  0  0  0  0
    2.2767    0.7899   -0.1658 C   0  0  1  0  0  0  0  0  0  0  0  0
    1.3052    1.8704   -0.4439 C   0  0  0  0  0  0  0  0  0  0  0  0
    0.0458    2.0072   -0.1342 C   0  0  0  0  0  0  0  0  0  0  0  0
   -0.6492    3.2462   -0.5802 C   0  0  0  0  0  0  0  0  0  0  0  0
   -0.8088    1.0601    0.6274 C   0  0  1  0  0  0  0  0  0  0  0  0
   -2.2842    1.2703    0.3678 C   0  0  0  0  0  0  0  0  0  0  0  0
   -2.8583   -0.0389    0.9265 C   0  0  0  0  0  0  0  0  0  0  0  0
   -1.8563   -1.1145    0.5132 C   0  0  2  0  0  0  0  0  0  0  0  0
   -2.4774   -1.8349   -0.6773 C   0  0  0  0  0  0  0  0  0  0  0  0
   -1.6400   -2.0267    1.5327 O   0  0  0  0  0  0  0  0  0  0  0  0
   -0.6447   -0.3683    0.0920 C   0  0  2  0  0  0  0  0  0  0  0  0
    0.6541   -0.9821    0.5402 C   0  0  0  0  0  0  0  0  0  0  0  0
    1.6915   -0.5888   -0.4406 C   0  0  2  0  0  0  0  0  0  0  0  0
    2.3134   -3.2791    0.2601 H   0  0  0  0  0  0  0  0  0  0  0  0
    4.1167   -3.0673   -0.1605 H   0  0  0  0  0  0  0  0  0  0  0  0
    2.7108    0.8539    0.8538 H   0  0  0  0  0  0  0  0  0  0  0  0
    1.7189    2.7123   -1.0158 H   0  0  0  0  0  0  0  0  0  0  0  0
   -0.3445    3.5519   -1.6030 H   0  0  0  0  0  0  0  0  0  0  0  0
   -1.7323    3.1907   -0.5061 H   0  0  0  0  0  0  0  0  0  0  0  0
   -0.3231    4.0490    0.1420 H   0  0  0  0  0  0  0  0  0  0  0  0
   -0.5692    1.0419    1.7056 H   0  0  0  0  0  0  0  0  0  0  0  0
   -2.4321    1.2881   -0.7283 H   0  0  0  0  0  0  0  0  0  0  0  0
   -2.7195    2.1039    0.9098 H   0  0  0  0  0  0  0  0  0  0  0  0
   -3.8639   -0.2459    0.5142 H   0  0  0  0  0  0  0  0  0  0  0  0
   -2.8591    0.0499    2.0278 H   0  0  0  0  0  0  0  0  0  0  0  0
   -1.6275   -2.0719   -1.3716 H   0  0  0  0  0  0  0  0  0  0  0  0
   -2.9546   -2.7781   -0.3829 H   0  0  0  0  0  0  0  0  0  0  0  0
   -3.1464   -1.1630   -1.2604 H   0  0  0  0  0  0  0  0  0  0  0  0
   -1.6000   -1.5952    2.4040 H   0  0  0  0  0  0  0  0  0  0  0  0
   -0.6702   -0.2514   -1.0260 H   0  0  0  0  0  0  0  0  0  0  0  0
    0.8717   -0.5476    1.5573 H   0  0  0  0  0  0  0  0  0  0  0  0
    0.5887   -2.0819    0.6567 H   0  0  0  0  0  0  0  0  0  0  0  0
    1.2404   -0.5455   -1.4558 H   0  0  0  0  0  0  0  0  0  0  0  0
  9  8  1  0
  8  7  2  0
  7  6  1  0
  6  5  1  0
  5  3  1  0
  3  4  2  0
  3  2  1  0
  2  1  2  3
  2 18  1  0
 18 17  1  0
 17 16  1  0
 16 10  1  0
 10 11  1  0
 11 12  1  0
 12 13  1  0
 13 14  1  0
 13 15  1  1
 10  8  1  0
 18  6  1  0
 13 16  1  0
  9 23  1  0
  9 24  1  0
  9 25  1  0
  7 22  1  0
  6 21  1  1
  1 19  1  0
  1 20  1  0
 18 38  1  6
 17 36  1  0
 17 37  1  0
 16 35  1  6
 10 26  1  1
 11 27  1  0
 11 28  1  0
 12 29  1  0
 12 30  1  0
 14 31  1  0
 14 32  1  0
 14 33  1  0
 15 34  1  0
M  END


  Mrv0541 05061305552D          

 18 20  0  0  0  0            999 V2000
    2.1276   -0.3907    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
   -0.1683    3.0467    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    2.3138    2.8852    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    3.1057    0.9236    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    3.4299    1.6822    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    0.9446    0.3526    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    1.3571    2.1599    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    1.7696    0.3526    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
   -0.0944    2.2250    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    2.2840    0.9976    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    0.6138    1.8019    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    2.1004    1.8019    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    0.4302    0.9976    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
   -0.7157    1.6822    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
    2.8086    2.2250    0.0000 C   0  0  0  0  0  0  0  0  0  0  0  0
   -1.5200    1.8658    0.0000 O   0  0  0  0  0  0  0  0  0  0  0  0
    3.4134    2.7862    0.0000 O   0  0  0  0  0  0  0  0  0  0  0  0
   -0.3914    0.9236    0.0000 O   0  0  0  0  0  0  0  0  0  0  0  0
  5  4  1  0  0  0  0
  8  1  1  0  0  0  0
  8  6  2  0  0  0  0
  9  2  2  0  0  0  0
 10  4  1  0  0  0  0
 10  8  1  0  0  0  0
 11  7  1  0  0  0  0
 11  9  1  0  0  0  0
 12  7  1  0  0  0  0
 12 10  1  0  0  0  0
 13  6  1  0  0  0  0
 13 11  1  0  0  0  0
 14  9  1  0  0  0  0
 15  3  1  0  0  0  0
 15  5  1  0  0  0  0
 15 12  1  0  0  0  0
 16 14  2  0  0  0  0
 17 15  1  0  0  0  0
 18 13  1  0  0  0  0
 18 14  1  0  0  0  0
M  END
> <DATABASE_ID>
NP0322298

> <DATABASE_NAME>
NP-MRD

> <SMILES>
CC1=CC2OC(=O)C(=C)C2CC2C1CCC2(C)O

> <INCHI_IDENTIFIER>
InChI=1S/C15H20O3/c1-8-6-13-11(9(2)14(16)18-13)7-12-10(8)4-5-15(12,3)17/h6,10-13,17H,2,4-5,7H2,1,3H3

> <INCHI_KEY>
APMKESKZWHNIDJ-UHFFFAOYSA-N

> <FORMULA>
C15H20O3

> <MOLECULAR_WEIGHT>
248.3175

> <EXACT_MASS>
248.141244506

> <JCHEM_ACCEPTOR_COUNT>
2

> <JCHEM_AVERAGE_POLARIZABILITY>
27.461302391934147

> <JCHEM_BIOAVAILABILITY>
1

> <JCHEM_DONOR_COUNT>
1

> <JCHEM_FORMAL_CHARGE>
0

> <JCHEM_GHOSE_FILTER>
1

> <JCHEM_IUPAC>
5-hydroxy-5,8-dimethyl-3-methylidene-2H,3H,3aH,4H,4aH,5H,6H,7H,7aH,9aH-azuleno[6,5-b]furan-2-one

> <ALOGPS_LOGP>
2.60

> <JCHEM_LOGP>
2.127713863

> <ALOGPS_LOGS>
-2.54

> <JCHEM_MDDR_LIKE_RULE>
0

> <JCHEM_NUMBER_OF_RINGS>
3

> <JCHEM_PHYSIOLOGICAL_CHARGE>
0

> <JCHEM_PKA_STRONGEST_ACIDIC>
19.779741678881813

> <JCHEM_PKA_STRONGEST_BASIC>
-0.7081406937391467

> <JCHEM_POLAR_SURFACE_AREA>
46.53

> <JCHEM_REFRACTIVITY>
68.8715

> <JCHEM_ROTATABLE_BOND_COUNT>
0

> <JCHEM_RULE_OF_FIVE>
1

> <ALOGPS_SOLUBILITY>
7.24e-01 g/l

> <JCHEM_TRADITIONAL_IUPAC>
5-hydroxy-5,8-dimethyl-3-methylidene-3aH,4H,4aH,6H,7H,7aH,9aH-azuleno[6,5-b]furan-2-one

> <JCHEM_VEBER_RULE>
0

$$$$

HEADER    PROTEIN                                 06-MAY-13   NONE
TITLE     NULL                                                        
COMPND    NULL                                                        
SOURCE    NULL                                                        
KEYWDS    NULL                                                        
EXPDTA    NULL                                                        
AUTHOR    Marvin                                                      
REVDAT   1   06-MAY-13         0                                  
HETATM    1  C   UNK     0       3.972  -0.729   0.000  0.00  0.00           C+0
HETATM    2  C   UNK     0      -0.314   5.687   0.000  0.00  0.00           C+0
HETATM    3  C   UNK     0       4.319   5.386   0.000  0.00  0.00           C+0
HETATM    4  C   UNK     0       5.797   1.724   0.000  0.00  0.00           C+0
HETATM    5  C   UNK     0       6.402   3.140   0.000  0.00  0.00           C+0
HETATM    6  C   UNK     0       1.763   0.658   0.000  0.00  0.00           C+0
HETATM    7  C   UNK     0       2.533   4.032   0.000  0.00  0.00           C+0
HETATM    8  C   UNK     0       3.303   0.658   0.000  0.00  0.00           C+0
HETATM    9  C   UNK     0      -0.176   4.153   0.000  0.00  0.00           C+0
HETATM   10  C   UNK     0       4.263   1.862   0.000  0.00  0.00           C+0
HETATM   11  C   UNK     0       1.146   3.364   0.000  0.00  0.00           C+0
HETATM   12  C   UNK     0       3.921   3.364   0.000  0.00  0.00           C+0
HETATM   13  C   UNK     0       0.803   1.862   0.000  0.00  0.00           C+0
HETATM   14  C   UNK     0      -1.336   3.140   0.000  0.00  0.00           C+0
HETATM   15  C   UNK     0       5.243   4.153   0.000  0.00  0.00           C+0
HETATM   16  O   UNK     0      -2.837   3.483   0.000  0.00  0.00           O+0
HETATM   17  O   UNK     0       6.372   5.201   0.000  0.00  0.00           O+0
HETATM   18  O   UNK     0      -0.731   1.724   0.000  0.00  0.00           O+0
CONECT    1    8                                                            
CONECT    2    9                                                            
CONECT    3   15                                                            
CONECT    4    5   10                                                       
CONECT    5    4   15                                                       
CONECT    6    8   13                                                       
CONECT    7   11   12                                                       
CONECT    8    1    6   10                                                  
CONECT    9    2   11   14                                                  
CONECT   10    4    8   12                                                  
CONECT   11    7    9   13                                                  
CONECT   12    7   10   15                                                  
CONECT   13    6   11   18                                                  
CONECT   14    9   16   18                                                  
CONECT   15    3    5   12   17                                             
CONECT   16   14                                                            
CONECT   17   15                                                            
CONECT   18   13   14                                                       
MASTER        0    0    0    0    0    0    0    0   18    0   40    0
END

View in JSmol

Synonyms

Not Available

Chemical Formula

C₁₅H₂₀O₃

Average Mass

248.3175 Da

Monoisotopic Mass

248.14124 Da

IUPAC Name

5-hydroxy-5,8-dimethyl-3-methylidene-2H,3H,3aH,4H,4aH,5H,6H,7H,7aH,9aH-azuleno[6,5-b]furan-2-one

Traditional Name

5-hydroxy-5,8-dimethyl-3-methylidene-3aH,4H,4aH,6H,7H,7aH,9aH-azuleno[6,5-b]furan-2-one

CAS Registry Number

Not Available

SMILES

CC1=CC2OC(=O)C(=C)C2CC2C1CCC2(C)O

InChI Identifier

InChI=1S/C15H20O3/c1-8-6-13-11(9(2)14(16)18-13)7-12-10(8)4-5-15(12,3)17/h6,10-13,17H,2,4-5,7H2,1,3H3

InChI Key

APMKESKZWHNIDJ-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
Apalochlamys spectabilis	LOTUS Database	35616633
Carpesium abrotanoides	LOTUS Database	35616633
Carpesium faberi	LOTUS Database	35616633
Dittrichia graveolens	LOTUS Database	35616633
Helichrysum dasyanthum	LOTUS Database	35616633
Inula caspica	LOTUS Database	35616633
Inula helenium	LOTUS Database	35616633
Pentanema britannicum	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
Cyclic alcohol
Tertiary alcohol
Tetrahydrofuran
Enoate ester
Alpha,beta-unsaturated carboxylic ester
Lactone
Carboxylic acid ester
Oxacycle
Monocarboxylic acid or derivatives
Carboxylic acid derivative
Organoheterocyclic compound
Organooxygen compound
Hydrocarbon derivative
Organic oxide
Organic oxygen compound
Alcohol
Carbonyl group
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	2.6	ALOGPS
logP	2.13	ChemAxon
logS	-2.5	ALOGPS
pKa (Strongest Acidic)	19.78	ChemAxon
pKa (Strongest Basic)	-0.71	ChemAxon
Physiological Charge	0	ChemAxon
Hydrogen Acceptor Count	2	ChemAxon
Hydrogen Donor Count	1	ChemAxon
Polar Surface Area	46.53 Å²	ChemAxon
Rotatable Bond Count	0	ChemAxon
Refractivity	68.87 m³·mol⁻¹	ChemAxon
Polarizability	27.46 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

HMDB0031378

DrugBank ID

Not Available

Phenol Explorer Compound ID

Not Available

FoodDB ID

FDB003445

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

12310399

PDB ID

Not Available

ChEBI ID

Not Available

Good Scents ID

Not Available

References

General References

LOTUS database [Link]

Showing NP-Card for 5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one (NP0322298)

MOL for NP0322298 (5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one)

3D MOL for NP0322298 (5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one)

3D SDF for NP0322298 (5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one)

3D-SDF for NP0322298 (5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one)

PDB for NP0322298 (5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one)

3D PDB for NP0322298 (5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one)

SMILES for NP0322298 (5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one)

INCHI for NP0322298 (5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one)

Structure for NP0322298 (5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one)

3D Structure for NP0322298 (5-hydroxy-5,8-dimethyl-3-methylidene-3ah,4h,4ah,6h,7h,7ah,9ah-azuleno[6,5-b]furan-2-one)