Iridoids from Carbohydrates via Pauson−Khand Reaction: Synthesis of Advanced Highly Oxygenated Cyclopentane-Annulated Pyranosides from d-Glucal Derivatives

Abstract
The Pauson−Khand reaction on suitable 4-oxa-hept-1-en-6-ynes (1, 17) obtained from 3,4,6-tri-O-acetyl-d-glucal gives the cyclopentane-annulated pyranosides (2, 18) that can be efficiently and stereoselectivelly transformed into chiral, advanced, highly oxygenated intermediates (10, 16, 24) for the synthesis of iridoid aglycones.