THE UNUSUAL REACTIVITY OF ,13]TRIDECAN-12-ONE-3-SPIRO-1'-CYCLOPENTAN-3'-ONES - A MOLECULAR MODELING STUDY

3)]tridecan-12-one-3-spiro-l'-cyclopentan-3'-ones, which are useful in termediates in the total synthesis of sesterterpenes, display an unusu al reactivity towards organometallic reagents in that the tetrahydrofu ran ring opening precedes the nucleophilic attack on the carbonyl grou p in the trans diastereoisomer 5. These experimental results, which ar e of considerable importance from a synthetic point of view, were rati onalized using molecular modelling techniques implemented using the AM PAC package. The different behaviour of the cis and trans diastereoiso mers is related to the steric strain of the tetrahydrofuran moiety in the latter compound.