THE CLAISEN REARRANGEMENT IN THE PREPARATION OF GEISSOSCHIZINE ISOMERS

The Claisen rearrangement of vinyl allyl ether 3 in refluxing toluene leads to a mixture of (+/-)-($) under bar Z-geissoschizine 5 and (+/-) -15-epi-($) under bar E-geissoschizine 6 [= (+/-)-3-epi-($) under bar E-geissoschizine 6'], whereas vinyl allyl ether 4, under the same reac tion conditions, affords only (+/-)-15-epi-($) under bar Z-geissaschiz ine 15 [= (+/-)3-epi-($) under bar Z-geissoschizine 15']. No (+/-)-($) under bar E-geissoschizine 16 was formed. However, the formation of ( +/-)-15-epi-($) under bar E-geissoschizine 6 [= (+/-)-3-epi-($) under bar E-geissoschizine 6'], which has earlier been transformed to (+/-)- ($) under bar E-geissoschizine 16, represents a new, formal total synt hesis of (+/-)-($) under bar E-geissoschizine 16. A conformational stu dy of the prepared compounds, mainly based on nmr measurements, is pre sented.