3- endo- -isoborneol

Steric effects are evident in the oxidation of sterically hindered alcohols exo-isoborneol is oxidized 2 times faster than endo-homeo], and endo-norborneol is oxidized 2.5 times faster than exo-norborneol (equation 248) [1145]. 

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] ... 

The hetero-Diels-Alder (HDA) reaction of 2,3-dimethylbuta-1,3-diene and cyclohexa-1,3-diene with ethyl glyoxylate catalysed by chiral Zn(II) complexes yields both the dihydropyran and the ene product, the former predominating. The enantiomeric excess, which can reach 87%, is dependent on the solvent as well as the catalyst <97JCS(P1)2345>. Use of (Rs,E)-3-[(15)-isoborneol-10-sulfinyl]-l-methoxybutadiene gives the 5,6-dihydropyran with good endo and facial diastereoselectivity <97TA2989>. Scandium(III) perfluoro-octanesulfonate is an efficient catalyst in the HDA reaction of aldehydes with non-activated dienes <97BCJ1421>. 

Koizumi and coworkers have developed a new enantiomerically pure a,p-unsaturated sulfoxide dienophile bearing the isoborneol group as a chiral auxiliary, dimethyl (f )-2-(10-isoborneolsulfinyl)maleate (214), which has been successfully employed as a chiral synthetic equivalent of dimethyl acetylenedicarboxylate [174], The dienophile (214) underwent cycloaddition with cyclopentadiene, in the presence of zinc chloride, with high stereo- and diastereoselectivity (92% single endo diastereoisomer, 6% single exo diastereoisomer) to yield the major cycloadduct (215), which was subsequently transformed into the half-ester (216), an intermediate in the syntheses of (-)-aristeromycin (199) and (-)-neplanocin A (200). Cycloadduct (215) has also recently been used for the synthesis of bicyclo[2.2.1]heptane lactone (217) [175,177], which itself is an intermediate in the synthesis of the iridoid (-)-boschnialactone [176] (218) (Scheme 5.69), and also in the formal synthesis of (-)-aristeromycin (199) and (-)-neplanocin (200) [177]. 

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... 

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