Isopulegole

General structural formula of the isopulegols without information on stereochemistry

The isopulegols are a group of monoterpenes that belong to the p -menthenols .

The eponymous compound isopulegol exists in two mirror-image forms, (-) - isopulegol and (+) - isopulegol.

Representative

As the representative of the isopulegols three asymmetric carbon atoms possess belong next to the Isopulegol- diastereomers and iso-isopulegol , neo-isopulegol and neoiso-isopulegol (each with its mirror-image isomers built) to the group of isopulegols.

In total there are eight stereoisomers , each two enantiomers of four different diastereomers :

(+) - and (-) - isopulegol,
(+) - and (-) - iso-isopulegol,
(+) - and (-) - Neo-Isopulegol and
(+) - and (-) - Neoiso-Isopulegol.

All eight compounds are colorless liquids.

Isopulegole
Surname	(+) - isopulegol	(-) - isopulegol	(+) - iso-isopulegol	(-) - Iso-Isopulegol	(+) - Neo-Isopulegol	(-) - Neo-Isopulegol	(+) - Neo-Iso-Isopulegol	(-) - Neo-Iso-Isopulegol
other names	(1 S , 2 R , 5 S ) -2-isopropenyl-5-methylcyclohexanol D -Isopulegol	(1 R , 2 S , 5 R ) -2-isopropenyl-5-methylcyclohexanol L -isopulegol	(1 S , 2 R , 5 R ) -2-Isopropenyl-5-methylcyclohexanol	(1 R , 2 S , 5 S ) -2-isopropenyl-5-methylcyclohexanol	(1 S , 2 S , 5 R ) -2-isopropenyl-5-methylcyclohexanol	(1 R , 2 R , 5 S ) -2-isopropenyl-5-methylcyclohexanol	(1 R , 2 R , 5 R ) -2-Isopropenyl-5-methylcyclohexanol	(1 S , 2 S , 5 S ) -2-isopropenyl-5-methylcyclohexanol
Structural formula
CAS number	104870-56-6	89-79-2	96612-21-4	18674-65-2	20549-46-6		144541-38-8
							21290-09-5 (±) -neoisoisopulegol
	7786-67-6 (mixture of isomers)
EC number	625-653-4	201-940-6
EC number	(Mixture of isomers)
ECHA ID	100.154.129	100.001.764
ECHA ID	(Mixture of isomers)
PubChem	1268090	170833	11008146		6553885
PubChem	24585 (mixture of isomers)
Wikidata object	Q27285994	Q2103922
Wikidata object	Q54727900 (mixture of isomers)
Molecular formula	C ₁₀ H ₁₈ O
Molar mass	154.25 g mol ⁻¹
Brief description	colorless liquids

Occurrence

(+) - and (-) - isopulegol

(+) - Neo-Isopulegol

(+) - Neoisopulegol has been detected in Mentha rotundifolia ( Lamiaceae ) and is also one of the components in Eucalyptus citriodora oil .

(+) - Neoiso-isopulegol

(+) - Neoiso-isopulegol was first isolated in 1960 from the mint oil of round-leaved mint ( Mentha rotundifolia ).

Natural extraction and synthesis

Eucaliptus ( Eucalyptus citriodora )

Natural extraction

Isopulegol can be obtained from a wide variety of plants, for example from the essential oils of Eucalyptus citriodora or lemongrass .

synthesis

It was first named in 1896 by Ferdinand Tiemann and R. Schmidt during the systematic investigation of the reactions of citronellal : "A cyclic alcohol, which we temporarily call isopulegol, is obtained from citronellal under the following conditions ..."

The substance can be obtained synthetically by catalytic cyclization (intramolecular Prins reaction of citronellal , also called intramolecular carbonyl-ene reaction). By choosing a suitable catalyst , the selectivity of the reaction for one or more stereoisomers of isopulegol can be increased. Typical catalysts are Lewis acids based on aluminum or silicon compounds , including zeolites such as clinoptilolite .

Individual evidence

↑ ^a ^b entry on p-menthenols. In: Römpp Online . Georg Thieme Verlag, accessed on June 7, 2016.
↑ Entry on eucalyptus oils. In: Römpp Online . Georg Thieme Verlag, accessed on June 7, 2016.
↑ Sumio Shimizua, Nagamori Ikedaa and Hiroo Uedaa: Isolation of (+) - Neoiso-isopulegol, a New Stereoisomer of Isopulegol and Piperitenone from a Variety of Mentha rotundifolia , Bull. Of the Agricult. Chem. Soc. Japan, Vol. 24, No. 3 (1960); doi : 10.1080 / 03758397.1960.10857672 .
^ BR Rajeswara Rao, PN Kaul, KV Syamasundar, S. Ramesh: Comparative composition of decanted and recovered essential oils of Eucalyptus citriodora Hook . In: Flavor and Fragrance Journal . tape 18 , no. 2 , 2003, p. 133-135 , doi : 10.1002 / ffj.1157 .
^ Raquel G. Jacob et al .: Green synthesis of ( -) - isopulegol from (+) - citronellal: application to essential oil of citronella . In: Tetrahedron Letters . tape 44 , no. 18 , 2003, p. 3605-3608 , doi : 10.1016 / S0040-4039 (03) 00714-7 .
↑ The specified conditions were: heating citronellal with acetic anhydride and subsequent saponification of the acetic ester purified by distillation. The structure of Pulegol is given in the article as the structure for this "Isopulegol" .
↑ Ferdinand Tiemann and R. Schmidt: About the connections of the citronellal series . In: Reports . tape 29 , no. 1 , January 1896, p. 903-926 , doi : 10.1002 / cber.189602901175 ( PDF ).
↑ US Patent 2117463: Method of producing isopulegol of May 17, 1938 to Charles O. Terwilliger
↑ Kelly A. da Silva et al .: Cyclization of (+) - citronellal to (-) - isopulegol catalyzed by H ₃ PW ₁₂ O ₄₀ / SiO ₂ , Catalysis Communications Vol. 5 No. 8 (2004), p. 425 -429; doi: 10.1016 / j.catcom.2004.05.001 .
↑ Mercedes Fuentes et al .: Cyclization of Citronellal to Isopulegol by Zeolite Catalysis , Applied Catalysis, vol. 47 no. 2, pp. 367-374 (1989); doi: 10.1016 / S0166-9834 (00) 83242-X .

[RömppMenthenole-1] try on p-menthenols. In: Römpp Online . Georg Thieme Verlag, accessed on June 7, 2016.

[RömppEucalyptusöle-2] Entry on eucalyptus oils. In: Römpp Online . Georg Thieme Verlag, accessed on June 7, 2016.

[3] Sumio Shimizua, Nagamori Ikedaa and Hiroo Uedaa: Isolation of (+) - Neoiso-isopulegol, a New Stereoisomer of Isopulegol and Piperitenone from a Variety of Mentha rotundifolia , Bull. Of the Agricult. Chem. Soc. Japan, Vol. 24, No. 3 (1960); doi : 10.1080 / 03758397.1960.10857672 .

[4] BR Rajeswara Rao, PN Kaul, KV Syamasundar, S. Ramesh: Comparative composition of decanted and recovered essential oils of Eucalyptus citriodora Hook . In: Flavor and Fragrance Journal . tape 18 , no. 2 , 2003, p. 133-135 , doi : 10.1002 / ffj.1157 .

[5] Raquel G. Jacob et al .: Green synthesis of ( -) - isopulegol from (+) - citronellal: application to essential oil of citronella . In: Tetrahedron Letters . tape 44 , no. 18 , 2003, p. 3605-3608 , doi : 10.1016 / S0040-4039 (03) 00714-7 .

[6] The specified conditions were: heating citronellal with acetic anhydride and subsequent saponification of the acetic ester purified by distillation. The structure of Pulegol is given in the article as the structure for this "Isopulegol" .

[7] Ferdinand Tiemann and R. Schmidt: About the connections of the citronellal series . In: Reports . tape 29 , no. 1 , January 1896, p. 903-926 , doi : 10.1002 / cber.189602901175 ( PDF ).

[8] US Patent 2117463: Method of producing isopulegol of May 17, 1938 to Charles O. Terwilliger

[9] Kelly A. da Silva et al .: Cyclization of (+) - citronellal to (-) - isopulegol catalyzed by H ₃ PW ₁₂ O ₄₀ / SiO ₂ , Catalysis Communications Vol. 5 No. 8 (2004), p. 425 -429; doi: 10.1016 / j.catcom.2004.05.001 .

[10] Mercedes Fuentes et al .: Cyclization of Citronellal to Isopulegol by Zeolite Catalysis , Applied Catalysis, vol. 47 no. 2, pp. 367-374 (1989); doi: 10.1016 / S0166-9834 (00) 83242-X .