Diels Alder synthetic routes, effect

A versatile synthetic route to enantiomeric ally pure Diels-Alder adducts was deduced and found dependent on the application of enantiomerically pure 5-methoxy-174a (R=Me) and 5-(l-menthyloxy)-2(5//)-furanones 174b (R = menthyl), which were expected to undergo tt-face-selective cycloaddition with dienes. The reaction was effected by heating no Lewis acid catalysts were required (Scheme 55) (88JOC1127). 

The intramolecular Diels—Alder (IMDA) reactions have a number of advantages over intermolecular reactions. They offer one of the most important synthetic routes for the stereoselective construction of polycyclic compounds. The presence of the diene and the dienophile together with a tether reduces the degree of freedom in the starting material. The length of the chain connecting the diene and the dienophile has a pronounced effect on the... 

---