Stereochemistry of diels-alder addition to levopimaric acid. Magnetic shielding by the carbon-carbon double bond

✍ Scribed by Walter L. Meyer; Robert W. Huffman

• Publisher: Elsevier Science
• Year: 1962
• Tongue: French
• Weight: 237 KB
• Volume: 3
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)70934-8

✦ Synopsis

DIELS

-Alder adducte of levopimaric acid (I) with many dienophiles are kn~wn.~ With symmetrical dienophiles, for example maleic anhydride, the reaction seems to he highly stereoselective, only one of four poseible isomers (IIa-d) being formed in high yield. Although it has been hypothesized, ad* 3 on the basis of the Alder rules' and steric hindrance by the angular methyl group to S-face approach of the dienophile, that the adduct corresponds to IIa, no evidence on this point has heretofore been reported. We wish to record such evidence. 1 Contribution No. 1044.