ABSTRACT
From the days of Emil Fisher, carbohydrates have played an important role in the development of organic chemistry [l]. Considering such a long historical relation and the remarkable progress made in the functional group manipulations of carbohydrates, studies aimed the usefulness of these compounds as a source of carbocyclic compounds are of recent origin. Most of the developments have appeared in the past 15 years or so, and several excellent reviews on the subject are available [2]. Carbohydrates, being the most ubiquitous source of chirality in nature, are ideal starting materials for many enantiomerically pure natural products [3], especially those that are highly oxygenated. Several biologically important compounds, such as antiviral carbocyclic nucleosides, macrocyclic antibiotics, aminocyclitol antibiotics, glycosidase inhibitors, inositols, and C-glycosides, are represented among this class of compounds [2b]. Historically, as with many other areas of organic chemistry, the first reported methods for the carbohydrate to carbocyclic conversions depended on carbanionic intermediates; the reader is referred to the excellent review by Ferrier [2a] and the references cited therein, for a detailed discussion on this subject. Typical among these methods are intramolecular alkylation and intramolecular condensations of aldehydes with enolates, phosphonate, and nitro-stabilized anions. Cycloaddition reactions, including intramolecular 1,3-dipolar additions and [4 + 2]-cyclo additions have also been used.
