Isobomeol, from camphor

Most synthetic camphor (43) is produced from camphene (13) made from a-piuene. The conversion to isobomyl acetate followed by saponification produces isobomeol (42) ia good yield. Although chemical oxidations of isobomeol with sulfuric/nitric acid mixtures, chromic acid, and others have been developed, catalytic dehydrogenation methods are more suitable on an iadustrial scale. A copper chromite catalyst is usually used to dehydrogenate isobomeol to camphor (171). Dehydrogenation has also been performed over catalysts such as ziac, iadium, gallium, and thallium (172). 

Isobomeol to Camphor. Nitric add has been widely used in the production of synthetic camphor from turpentine. The commonly accepted general practice for this manufacture (the one adapted by Gubehnann fw use in this country) involves the following steps (1) distillation of turpentine to obtain pinene, (2) saturation with HCl gas to obtain bomyl chloride, (3) hydrolyzing this to obtain camphene, (4) esterifying camphene to isobomyl acetate, (5) saponification to isobomeol, and (6) oxidation to camphor. 

Bomeol, isobomeol, and camphor are the most important members of the bomane (camphane) family of bicyclic monoterpenes. The labeling pattern of borneol and camphor derived from exogenous [2- C]mevalonate and [2- K jgeraniol in intact tissue is consistent with Ruzicka s hypothesis (Fig. 5) (Banthorpe and Baxendale, 1970 Battersby et al., 1972). Soluble enzyme preparations from sage leaves convert [1- H]NPP to (-t-)-[3- H]bomeol in the presence of Mg and, in the presence of NAD, dehydrogenate the bomeol to (-t-)-[3- H]camphor (Croteau and Karp, 1976b). [1- H]GPP was a less efficient precursor of borneol and camphor in this crude preparation. The epi-... 

Sublimation is a faster method of purification than crystallization but not as selective. Similar vapor pressures are often a factor in dealing with solids that sublime consequently, little separation can be achieved. For this reason, solids are far more often purified by crystallization. Sublimation is most effective in removing a volatile substance from a nonvolatile compound, particularly a salt or other inorganic material. Sublimation is also effective in removing highly volatile bicyclic or other symmetrical molecules from less volatile reaction products. Examples of volatile bicyclic compounds are borneol, isobomeol, and camphor. 

Camphor [126-04-5] (11), menthol [89-78-1] (12), and thymol [89-83-8] (13) ate used in topical over-the-counter cough and cold preparations. Camphor is isolated from the camphor tree, Cinnomomum camphora T. Nees Eherneier, or prepared synthetically from a-pinene or isobomeol. About 75% of the camphor sold in the United States is synthetic. Menthol, commercially the most important terpene alcohol, is obtained by crysta11i2ation from... 

Figure 2.5 Reported concentrations of various PPCPs in Wastewater effluents by several research groups. On the x axis are respective PPCPs that are primarily cosmetics (1 = HHCB, 2 = AHTN, 3 = acetophenone, 4 = camphor, 5 = isobomeol, 6 = skatol, 7 = celestolide, i.e., AHMI, 8 = Phantolide, i.e., AHMI), the lotion ingredient (9 = methyl salicylate), two disinfectants (10 = triclosan and 11 = trilocarban), antihypertensive (12 = dehydronifedipine, 13 = diltiazem, 14 = bezafibrate, and 15 = gemfibrozil), analgesics and anti-inflammatories (16 = naproxen, 17 = ibuprofen, 18 = codeine), antimicrobials (19 = chlortetracycline, 20 = erythromycin, 21 = novobiocin, 22 = oxytetracycline, 23 = sulfamethaxazole, 24 = thiabendazole, 25 = trimethoprim), anxiolytic sedative (26 = carbamazepine), antidiabetic (27 = metaformin), reproductive (28 = 17(3 estradiol, 29 = 17a-ethinyl estradiol), GIT (30 = cimetidine, 31 = ranitidine), and respiratory (32 = Albuterol). The concentrations were compiled from Boyd et al. (2003), Gagne et al. (2006), Glassmeyer et al. (2005), Halden and Pauli (2005), Huang and Sedlak (2001), Ricking et al. (2003), and Temes et al. (2003).

Cyclopentane bicyclic monoterpenoids that occur in the plant kingdom belong to three major skeletal types camphane, iso-camphane, and fenchane (Fig. 7). Camphane-type terpenoid alcohols, (+)-bomeol (Gl) and (—)-isobomeol (G2), have been isolated from Cinnamomum camphora (Lauraceae) and Achillea filipendulina (Asteraceae). A ketone derived from these, (-h)-camphor (G3), is found in the camphor tree Cinnamomum camphora) and in the leaves of rosemary Rosmarinus officinalis) and sage Salvia officinalis, Labiatae). Camphene (G4) and its enantiomer with the isocamphane carbon skeleton are known to occur in the oils of citronella and turpentine. Fenchane-type bicyclic cyclopentane monoterpenoids are commonly found in plants as their ketone derivatives. (—)-Fenchone (G5) occurs in the tree of life Thuja occidentalis, Cupres-saceae). Its enantiomer, (+)-fenchone (G6), has been isolated from the oil of fennel Foeniculum vulgare, Umbelliferae). 

Bifimctional catalytic composites consisting in poly(vinyl alcohol) crosslinked with sulfosuccinic acid and Co(acac)2 complex or Co(acac)2trien encaged in NaY zeolite dispersed in the polymeric matrix, are active catalysts for the hydration of camphene and oxidation of isobomeol, making possible the one pot synthesis of camphor from camphene. The way as the Co complex is immobilised in the polymer matrix, directly or entrapped in zeolite Y, leads to opposite effects in the catalytic activity, probably due to the competition between transport and sorption phenomena. 

Isobomeol dissolved in benzene or chloroform is readily oxidized to camphor with chlorine. Thus, a solution of 15.4 parts of isobomeol dissolved in 16 parts of benzene is shaken violently with a solution of 7.1 partili of chlorine dissolved in 900 parts of water by weight. Violent agitation is necessary to secure intimate contact of the two immiscible solutions. Camphor is recovered from the benzene solution after reaction is complete, in almost quantitative yield, and contains only traces of chlorine. Use of alkaline aqueous solutions of chlorine results in the formation of sodium chloride as a by-product. 

With ketones that are locked due to a bridged ring system, then it is normally straightforward to predict which is the less-hindered side of the carbonyl group. Reduction of camphor with lithium aluminium hydride, for example, leads mainly to the exo alcohol (isobomeol), whereas norcamphor (which lacks the gem-dimethyl group on the bridging carbon atom), in which approach of the hydride anion is now easier from the side of the methylene bridge, leads mainly to the endo alcohol. 

Naturally occurring camphanes include the bomeols with an endo hydroxy group, the isobomeols with an exo OH and 2-camphanone (2-bonanone) referred to as camphor. (+)-Bomeol from the camphor tree Cinnamomum camphora (Lauraceae) and from the roots of ginger-like Curcuma aromatica (Zingiberaceae), both of which grow in Eastern Asia, is known as Borneo camphor. (-)-Isobomeol was isolated from Achillea filipendulina (Asteraceae). 

Part C. Percentages ot Isobomeol and Borneol Obtained from the Reduction of Camphor... 

Your instructor will advise you of the method you should use to analyze the products from the sodium borohydride reduction of camphor. Each method yields the percentages of isobomeol and borneol obfained. 

The preparation and uses of isobomeol (119) and its esters are described above in section Bicyclic Monoterpeniod Hydrocarbons under camphene. Optically pure (—)-bomeol can also be prepared from (—)-pinenes (277). Bomeol, isobomeol, and their acetates occur in a wide variety of herbs and other plants. They are used in perfumes for soaps and detergents for woody, camphor, and pine notes with a relatively low cost. Two monoethers of... 

Most synthetic camphor is produced from a-pinene (20) via camphene (27), as shown in Fig. 8.24. Addition of acetic acid to camphene gives isobomyl acetate (117), which is saponified to produce isobomeol (119) in good yield. Catalytic dehydrogenation of iso-borneol then gives camphor. Catalysts include copper chromite (319) or metals, such as zinc, indium, gallium, and thallium (320). 

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