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Paper | Special issue | Vol 67, No. 1, 2006, pp.291-298
Published online, 30th August, 2005
DOI: 10.3987/COM-05-S(T)26
New Routes to Clavine-type Ergot Alkaloids. Part 1. First Total Synthesis of Three Natural Products: (+)-Setoclavine, (+)-Isosetoclavine, (-)-9,10-Dihydroisosetoclavine, and Structure Correction of the Latter

István Moldvai,* Eszter Temesvári-Major, Eszter Gács-Baitz, Mária Incze, Gábor Dörnyei, and Csaba Szántay*

*Institute of Chemistry, Chemical Research Center, Hungarian Academy of Sciences, H-1525 Budpest II, Pusztaszeri ut 59-67, P.O. Box 17, Hungary

Abstract

The double bond in ring D of (+)-9,10-didehydro-6-methylergolin-8-one (2) was reduced selectively by catalytic hydrogenation to yield (-)-6-methylergolin-8-one (6). Grignard reaction of 6 has been performed with methylmagnesium iodide to afford two isomers (5 and 7). The main isomer having an 8α-methyl group at C8 with a C/D-trans junction (5; (-)-dihydro-isosetoclavine) proved to be identical with the natural product, hence its name and structure should be corrected. As a minor isomer (7) a C/D-cis clavine derivative was also isolated which can be regarded as unnatural (+)-8α-hydroxy-costaclavine. (+)-Setoclavine (8) and (+)-isosetoclavine (9) have also been prepared from 2, thus achieving the first total synthesis of these natural products. Detailed structure elucidation of 5-9 has been carried out as well.