The bioreduction of a series of substituted a-tetralones, carried out using Daucus carota root (carrot), afforded the corresponding homochiral a-tetralols in variable conversions (9 to 90%) and excellent enantiomeric excesses. Two of the assayed a-tetralones were resistant to the bioreduction conditions. The absolute configurations of four a-tetralols were assigned as being (S), by comparison to the (S)-enantiomers obtained by kinetic resolution promoted by CALB-catalysed acetylation. Additionally, the new 5-methoxy-6-methyl-1-tetralone was synthesized in seven steps from 3-methylsalicylic acid.

The natural occurrence, biological activities and synthetic approaches to natural eight-, nine-, and eleven-membered lactones is reviewed. These medium ring lactones are grouped according to ring size, and their syntheses are discussed. The structures of some natural products early identified as medium-ring lactones were revised after total synthesis.

There are several natural products bearing medium ring lactone moieties, which are those containing a ring size in the range of 8 to 11 members. This review intends to cover the last 10 years (1996-2005) of the literature concerning the synthesis of medium ring lactones.

Este trabalho descreve a reação de desidroiodação, promovida por base, de uma série de beta-iodo-enol éteres cíclicos. Os produtos são tetraidrofuranos contendo duas ligações duplas exocíclicas, di- e tetraidrobenzofuranos e um derivado de diidropirano, todos obtidos em ótimos rendimentos.

This work describes the base-promoted dehydroiodination of differently substituted cyclic beta-iodo-enol ethers. The products are tetrahydrofuran derivatives bearing two exocyclic double bonds, di- and tetrahydrobenzofurans and a dihydropyran derivative, which were obtained in very good yields.