The present invention concerns a process for preparing each of the 4
individual diastereomers of formula (I) in stereochemically pure form
from a single enantiomerically pure precursor. The tetracyclic ringsystem
having cis-fused five and seven membered rings is formed in a
base-catalysed cyclization reaction. The invention further relates to the
thus obtained cis-fused tetracyclic alcohol intermediates and methanamine
end-products, and the methanamine end-products for use as a medicine, in
particular as CNS active medicines. 1
