Short and efficient syntheses of gabosine I, streptol, 7-O-acetylstreptol, 1-epi-streptol, gabosine K, and carba α-d-glucose from δ-d-gluconolactone

δ-d-Gluconolactone was carbocyclized into an EOM-protected cyclohexenone in four steps involving perethoxymethylation, phosphonate anion addition, reduction, and oxidation with concomitant Horner-Wadsworth-Emmons alkenation. The stable key enone was efficiently transformed into gabosine I (five steps with 65% overall yield from δ-d-gluconolactone), streptol (six steps, 54% overall yield), 7-O-acetyl-streptol (seven steps, 42% overall yield), 1-epi-streptol (six steps, 49% overall yield), gabosine K (seven steps, 40% overall yield), and carba - d-glucopyranose (seven steps, 47% overall yield). The present chemical syntheses, from commercially available δ-d-gluconolactone, provide the highest overall yields of these molecules to date.