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Treatment of D-glucose-derived alkene 4 with cyclopentadiene in the presence of a Lewis acid results in the formation of cycloaddition products 8-11. Evidence is presented to show that these 1,6-anhydro sugar-cyclopentadiene adducts do not arise from rearrangement of 4 to isolevoglucosenone (5) followed by cycloaddition but are the result of Lewis acid-catalyzed rearrangement of alkene 4 to acyclic dienophile 12 followed by addition of cyclopentadiene. Major cycloadduct 8 has been utilized as a source of the enantiomerically pure carbocycles 14-25 by manipulation of the alkene and ketone functions and cleavage of the 1,6-anhydro bridge. In the absence of diene, alkene 4 undergoes rearrangement to enone 5 in 32% yield. Reaction of 5 with several dienes results only in the formation of "bottom-face" adducts 10,11, 28, and 29, and conjugate addition of either HN(3) or Me(3)COOH is found to be completely stereoselective to afford 30 and 31, respectively. Subsequent manipulation of azide 30 leads to precursors of several naturally occurring 2-amino-2,3-dideoxy sugars.

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Stereospecific S N 2 conversion of configurationally pure acetobromoglucose (2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide) to the corresponding β-Dglucopyranosyl azide is a useful exercise in the advanced organic undergraduate teaching laboratory. The procedure is safe and suitable for small-scale implementation, and firm proof of the stereochemical change is obtained from 1 H NMR coupling constants. The exercise provides students with experience in using important chiral pool natural product derivatives, reaction analysis by TLC, as well as careful product isolation, purification, and spectroscopic identification.