Isopulegol synthesis

Nakatani Y, Kawashima K (1978) A highly stereoselective preparation of 1-isopulegol. Synthesis 147-148... 

Lewis acids, results in the formation of isopulegol (43) with greater than 98% diastereoselectivity isopulegol (43), wherein all of the ring substituents are equatorially oriented, arises naturally from a chairlike transition state structure in which the C-3 methyl group, the coordinated C-l aldehyde carbonyl, and the A6,7 double bond are all equatorial (see 48). A low-temperature crystallization raises the chemical and enantiomeric purity of isopulegol (43) close to 100%. Finally, hydrogenation of the double bond in 43 completes the synthesis of (-)-menthol (1). 

Isopulegol, 24 517-519, 526 Isoquinoline. See also Isoquinolines reduction of, 27 201 uses for, 27 206-208 Isoquinoline derivatives. See also Isoquinolines drugs, 27 207—208t synthesis of, 27 201-206 uses for, 27 206-208 Isoquinoline TV-oxide, 27 200-201 Isoquinolines, 27 182, 200-208 alkyl, 27 205... 

The total synthesis of artemisinin via conventional chemistry has also been achieved. In 1983, Schmid and Hofheinz pubhshed a paper showing the complete synthesis of artemisinin from (-)-Isopulegol (Scheme 10), with 5% overall yield. Since then, several other total synthesis of arteminisin... 

Hong and co-workers have described a formal [3-t-3] cycloaddition of a,P-unsaturated aldehydes using L-proline as the catalyst (Scheme 72) [225], Although the precise mechanism of this reaction is unclear a plausible explanation involves both iminium ion and enamine activation of the substrates and was exploited in the asymmetric synthesis of (-)-isopulegol hydrate 180 and (-)-cubebaol 181. This strategy has also been extended to the trimerisation of acrolein in the synthesis of montiporyne F [226],... 

Scheme 72 Iminium ion catalysed [3+3] addition in the synthesis of isopulegol hydrate and cubebaol...

The intramolecular carbonyl ene reaction is a useful way to generate a C-C bond and has been well studied [49-52]. Of particular interest is the cyclization of citronellal to yield isopulegol, an important intermediate in an industrial synthesis... 

Isoproterenol, chemiluminescence, 647 (—)-Isopulegol, artemisinin synthesis, 277, 278 Isothermal microcalorimetry, oxidation stability evaluation, 672 Isotopomers... 

Pure citronellal is a colorless liquid with a refreshing odor, reminiscent of balm mint. Upon catalytic hydrogenation, citronellal yields dihydrocitronellal, citro-nellol, or dihydrocitronellol, depending on the reaction conditions. Protection of the aldehyde group, followed by addition of water to the double bond in the presence of mineral acids or ion-exchange resins results in formation of 3,7-dimethyl-7-hydroxyoctan-l-al (hydroxydihydrocitronellal). Acid-catalyzed cycli-zation to isopulegol is an important step in the synthesis of (-)-menthol. 

Isocyanophosphonates, aldol reactions, 227 Isoquinoline synthesis, enamide reactions, 33 Isomerization allylic amines, 9, 95 olefins, 118, 171 see also specific compounds Isopulegol, 102 Isotactic polymers, 174 chloral, 182 photoirradiation, 347 methacrylates, 181 propylene, 174 Isotacticity, 177... 

The palladium [Pd(Ph3)4]-catalysed 3 + 3-cycloaddition of trimethylenemethane with azomethineimines produced hexahydropyridazine derivatives under mild conditions (40 °C).171 The Lewis acid-catalysed formal oxa-[3 + 3]-cycloaddition of a,f+ unsaturated aldehydes with 6-methyl-4-hydroxy-2-pyrone, 1,3-diketones, and viny-logous silyl esters yielded a variety of pyrones at room temperature.172 Croton-aldehyde has been converted to 6-hydroxy-4-methylcyclohex-l-enecarboxaldehyde by an enantioselective 3 + 3-cycloaddition catalysed by proline. This methodology was used in the synthesis of (—)-isopulegol hydrate, (—)-cubebaol, and (—)-6-hydroxy-4-methylcyclohex-l-ene-1-methanol acetate, an intermediate in the total synthesis of the alkaloid magellanine.173... 

Moreira, J.A. and Correa, A.G. (2003). Enantioselective synthesis of three stereoisomers of 5,9-dimethylpentadecane, sex pheromone component of Leucoptera coffeella, from (-)-isopulegol. Tetrahedron Asymm., 14, 3787-3795. 

The terpene menthol is widely used in organic synthesis, and serves as a chiral auxiliary for several asymmetric reactions [39]. (-)-Menthol 53 could be produced in one step from isopulegol 55 by hydrogenation of the carbon-carbon double bond, and the latter compound could be prepared by a Lewis acid-induced carbonyl-ene reaction [40] of f-(y )-citronellal 54. Nakatani and Kawashima examined that the ene cyclization of citronellal to isopulegol with several Lewis acids in benzene (Sch. 22) [41]. The zinc reagents were far superior to other Lewis acids for obtaining... 

The key intermediate for the synthesis of artemisinine is the acid 80, which has been used to build-up the peroxide linkage resulting in the formation of 7. Schmid and Hofheinz [92] obtained 80 starting from (-)-isopulegol (72) (Scheme 7), while the Chinese scientists have synthesized it starting from R(+)-citronellal (81) (Scheme 8) [93]. 

Due to the interest in substituting mineral and Lewis acids in the synthesis of fine chemicals to avoid inorganic salts production, and in order to have a deeper insight into the acidic properties of our catalysts, we investigated the behaviour of the supports, in a typical acid catalyzed reaction [7], namely the ene reaction of citronellal to give the four isopulegol isomers. 

The evodone synthesis reported in Vol. 2, p. 33, has been published again. Menthenolides have been synthesized by Tadwalkar and Rao. cis-Isopulegol acetate gives the lactone (196), and by the same route ns-pulegol (179) was con-vertedinto(197).203... 

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