Borneol and isoborneol

The following table exhibits the principal difference between borneol and isoborneol —... 

Camphene hydrate is a tertiary alcohol, and a study of its characters and method of preparation caused Aschan to consider that it is improbable that borneol and isoborneol are stereoisomeric, but that they probably have different constitutional formulae. 

Bicyclic cyclopropyl compounds are anodically dimethoxylated to give stereoisomeric cis and trans) cyclopropane ring-opened products, as in Eq. (48) [322]. Shono and coworkers [323] reported a different type of ring-opening reaction of a cyclobutyl compound through anodic methoxylation. They also found that anodic oxidation of borneol and isoborneol in methanol resulted in a rearrangement to provide methoxylated stereoisomeric products with the same endo-exo ratio, as in Eq. (49) [324] ... 

H. Firouzabadi and E. Ghaderi, Tetrahedron Letters, 1978, 839 the borneols [a mixture of (+)-borneol and (—)-isoborneol was used] and camphor each lack the C-10 methyl group in this paper. 

USE Primarily in the manuf of its esters. Some free borneol and isoborneol is used in perfumery and in incense making. Caution May cause nausea, vomiting, mental... 

In the elimination of HOTs from exo-2-norbornyl tosylate using the sodium salt of 2-cyclohexylcyclohexanol in triglyme at 80 °C, syn-exo elimination is at least 100 times faster than anti elimination. If 18-crown-6 is added, the rate ratio falls to ca. 15 1, indicating that the presence of the sodium cation is important in the complex transition state of the syn process. Pyrolysis of urethanes of borneol and isoborneol has been re-examined and found to give mixtures including a-pinene, tricyclene, camphene, and alcohols. Pyrolysis of nitrobenzoates gives no alcohols but camph-ene, tricyclene, and bornene. ... 

Camphor, a bicyclic monoterpene, is extracted from the woods of Cinnamomum camphora, a tree located in Southeast Asia and North America. Furthermore, it is also one of the major constituents of the essential oil of common sage (Salvia officinalis). Solid camphor forms white, fatty crystals with intensive camphoraceous odor and is used commercially as a moth repellent and preservative in pharmaceuticals and cosmetics (Wichtel, 2002). In dogs, rabbits, and rats, camphor is extensively metabolized whereas the major hydroxylation products of d- and L-camphor were 5-endo-md 5-ex -hydroxycamphor. A small amount was also identified as 3-e do-hydroxycamphor (Figure 8.2). Both 3- and 5-bornane groups can be further reduced to 2,5-bornanedione. Minor biotransformation steps also involve the reduction of camphor to borneol and isoborneol. Interestingly, all hydroxy-lated camphor metabolites are further conjugated in a Phase II reaction with glucuronic acid... 

Diastereo- and enanhoselechve dehydrogenahon is observed in carveol, borneol, and isoborneol... 

Camphor, Cj HjgO, occurs in the wood of the camphor tree Laurus camphora) as dextro-camphor. This is the ordinary camphor of commerce, known as Japan camphor, whilst the less common laevo-camphor is found in the oil of Matricaria parthenium. Camphor can also be obtained by the oxidation of borneol or isoborneol with nitric acid. Camphor may be prepared from turpentine in numerous ways, and there are many patents existing for its artificial preparation. Artificial camphor, however, does not appear to be able to compete commercially with the natural product. Amongst the methods may be enumerated the following —... 

A vast array of chiral auxiliaries have been derived from naturally occurring compounds containing the bicyclo[2.2.1]heptane unit (for review articles, see refs 1 -3). In all cases, the ultimate sources of these auxiliaries are the ketones camphor and fenchone, and the alcohols borneol and fenchol, as at least one enantiomer of each compound is provided in enantiomericaUy pure form by nature. Thus. ( + )-camphor [( + )-2], (-)-borneol [(-)- ], and (+)-fenchonc [( + )-5] are enan-tiomerically pure, convenient and inexpensive starting materials for organic synthesis and deriva-tization to give chiral auxiliaries. Most other compounds of this series are also commercially available, but can be prepared by oxidation or reduction of inexpensive precursors by standard methods. The evo-alcohols, such as the enantiomeric isoborneols, are accessible by standard complex hydride reductions of the ketones. The interconnection between these compounds is shown diagrammatically. 

The structure of the bicychc monoterpene borneol is shown in Figure 26 7 Isoborneol a stereoisomer of borneol can be prepared in the labora tory by a two step sequence In the first step borneol is oxidized to camphor by treatment with chromic acid In the second step camphor is reduced with sodium borohydride to a mixture of 85% isoborneol and 15% borneol On the basis of these transformations deduce structural formulas for isoborneol and camphor... 

Buchbauer G, Jager W, Jirovetz L, Meyer F, Dietrich H. (1992). [Effects of valerian root oil, borneol, isoborneol, bornyl acetate and isobornyl acetate on the motility of laboratory animals (mice) after inhalation]. Pharmazie. 1992 Aug. 47(8) 620-2. 

Bomeol is a colorless, crystalline solid. (+)-Borneol has a camphoraceous odor, with a slightly sharp, earthy-peppery note, which is less evident in (—)-bomeol. Commercial bomeol is often levorotatory ([ajp — 18 to — 28° in ethanol), and contains (—)-bomeol and up to 40% isoborneol. 

By isomerisation, a-pinene can be converted into camphene, and this can then be esterified to obtain an ester of isoborneate, which can be saponified to isoborneol. Isoborneol can be dehydrogenated to camphor, which can be reduced again to borneol, which is used in many fruit flavours. 

In the case of cinnamyl alcohol, menthol, borneol, isoborneol, cholesterol, and benzoin, the alcohol is dissolved in approximately 10 ml of ligroin before it reacts with a-naphthyl isocyanate. 

Method A To an ice-cold solution of 8.0 g (0.06 mol) of anhyd AICI, in 60 mL of F.t,0 are added 15 mL (0.015 mol) of a 1 M ethereal soln of LiAIH4. After a few minutes, 9.3 g (0.06 mol) of (—)-isoborneol (or borneol) in 1 5 mL of Ei,0 is added dropwise until the evolution of gas ceases. A slight excess of the alcohol is generally used to avoid any unreacted hydride. The reaction vessel is removed from the ice-bath and 0.05 mol of the ketone in 20 mL of F.t,0 is added within 15 min. The mixture is stirred at r.t. for 30 min and then cautiously decomposed with icc-cold 4 N H2SG4. The ethereal layer is separated, washed free of mineral acid and the solvent is evaporated through a Vigreux column. The crude products are analyzed by GC. For results and yields see Table 8, entries 1-68. 

---