Pentacydic compounds

The combination of a Stille and a Diels-Alder reaction has also been used for a derivatization of steroids, for example, in the synthesis of pentacydic compounds such as 6/1-189, as described by Kollar and coworkers [97]. Reaction of 17-iodoan-drosta-16-ene 6/1-187 with vinyltributyltin and various dienophiles such as diethyl... 

These results substantiate the mechanism that pentacydic compounds (12x) are derived from the tautomeric isomer (7x) by way of the semibuUvalene intermediate (15x) followed by rearrangement to pentalenopyrimidine (16x). Thus, the present work demonstrates that pentacyclo[6.4.0.0. > 0. 0 ]dodecanes (3x)... 

In a similar way, enetetraynes can undergo a pentacydization as observed for compound 6/1-272, which gave 6/1-273 in 66% yield (Scheme 6/1.72). In this case... 

Nagasawa, K., Georgieva, A., and Nakata, T. (2000) Practical and stereoselective synthesis of a pentacydic guanidine system Synthetic studies toward ptilomycalin A and related compounds. Tetrahedron, 56,187-192. 

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