Proto-Quercitol, synthesis

The deoxyinositols (quercitols, cyclohexanepentols) are useful model compounds which display many of the physical and chemical properties of true deoxy sugars. Although (-b)-proto-quercitol, the best known isomer, was isolated from nature 118 years ago, no synthesis has been reported up until now. The synthesis here described is actually that of the (-)-enantiomer, starting with (-)-inositol however, identical procedures applied to the readily available ( + ) or dl-inositol would give (- -) or DL-proto-quercitol, respectively. The natural occurence of, )-proto-quercitol has... 

The Synthesis of (— -proto-Quercitol, Although proto-quercitol (dextro) was discovered in 1849 ( 5), its cyclohexanepentol structure was not established until 1885 (13), and its configuration not until 1932. (38). The synthesis of this well-known cyclitol has been a difficult problem, since it appears that nearly every synthetic reaction commonly employed for other cyclitols would lead stereospecifically to the wrong product. 

It was not until 1966 that the synthesis of proto-quercitol (levo) was finally accomplished (30) by indirect removal of the position 2 hydroxyl group in (—) -inositol (14). 

The identical synthetic procedures applied to ( + )-inositol or dl-inositol should lead to ( + )-proto-quercitol and DL-proto-quercitol, respectively. Since the total synthesis of DL-inositol had previously been reported (33), the new syntheses of the various forms of proto-quercitol are total, with the possible exception of the step for resolution of DL-inositol, which so far has been accomplished only by a microbiological method (43). 

Salamci, E., Secen, H., Siitbeyaz, Y. and Bald, M. (1997) A condse and convenient synthesis of dl-proto-quercitol and dl-golo-quercitol via ene reaction of singlet oxygen combined with [2 + 4] cycloaddition to cyclohexadiene. Journal of Organic Chemistry, 62 (8), 2453-2457. 

Salamci, E., Secen, H., Sutbeyaz, Y., Balci, M., A Concise and Convenient Synthesis of dl proto Quercitol and dl gala Quercitol via Ene Reaction of Singlet Oxygen Combined with [2 + 4] Cycloaddition to Cyclohexadiene, J. Org. Chem. 1997, 62, 2453 2457. 

Mild oxidation of quercitols gives ketotetrols (or, occasionally, diketo-triols), and is achieved by the use of Acetobacter suhoxydans, - - catalytic oxygenation, or a halogen. Catalytic oxidation of mwco-quercitol is the first step in a reported synthesis of the antibiotic degradation product, 2-deoxystreptamine (better named 5-deoxystreptamine). Acetobacter studies on the cis, neo, proto, scyllo, and vibo isomers have been reported. Most halogen-oxidation products have not been well characterized. 

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