203924-94-1Relevant articles and documents
Stereoselective synthesis of polysubstituted tetrahydrofurans by radical cyclization of epoxides using a transition-metal radical source. Application to the total synthesis of (±)-methylenolactocin and (±)-protolichesterinic acid
Mandal,Maiti,Roy
, p. 2829 - 2834 (2007/10/03)
Radical cyclization reactions of substituted α-(prop-2-ynyloxy) epoxides using bis(cyclopentadienyl)-titanium(III) chloride as the radical source resulted in polysubstituted tetrahydrofurans. Titanium(III) species were prepared in situ from commercially available titanocene dichloride and zinc dust in tetrahydrofuran. Upon radical cyclization, 2-aryl epoxides 3a-e afforded only trans products 4a-e whereas the 2-alkyl epoxides 3f-h formed a mixture of isomeric products 4f-h in a ratio of 5:1. Some of the aryl tetrahydrofuran derivatives have already been used for the synthesis of bioactive furofuran lignans. 2-Pentyl-3-(hydroxymethyl)-4- methylenetetrahydrofuran (4f) and 2-tridecyl-3-(hydroxymethyl)-4- methylenetetrahydrofuran (4g) have been transformed to two antitumor antibiotics (±)-methylenolactocin (1f) and (±)-protolichesterinic acid (1g), respectively, in good overall yield.
