Synthesis polyfunctional polycyclic

ACS Symposium Series Ameriean Chemieal Soeiety Washington, DC, 1977. 

SECS 2.4 occupies 130K 32-bit words of memory, but when overlayed fits in 48K. Additionally the program uses about IM bytes of auxiliary disk storage for permanent and temporary files. SECS is written in FORTRAN IV and runs on PDP-10, 

MOLECULE NAME (A20) TEST ENTER NUMBER OF NEW ATOMS 5 

TO CREATE BONDS, TYPE BOND PATHS END WITH BLANK LINE BONDS 123452 BONDS 4 5 

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The chemistry of the diterpenoid alkaloids, rather than their structure elucidation by physical methods, has attracted more interest during the year covered by this Report. While several new alkaloids have been reported, most of the research on these polycyclic, polyfunctional bases has involved chemical conversions and synthetic methods. Most notably, Wiesner s group at New Brunswick, Canada, has reported a fourth-generation synthesis of the delphinine-type alkaloids. That this marvel of synthetic engineering accomplishes the stated goals1 of a highly efficient, fully regio- and stereo-specific synthesis of these complex natural products is abundantly clear. 

An additional advantage of the intramolecular protocol stems from the opportunity to prepare easily the required polyfunctional precursors via cobalt carbonyl stabilized propargyl cations. The approach based on the tandem utilization of Co-mediated alkylation and Pauson-Khand annulation was developed in Schreiber s studies to elaborate short pathways for the synthesis of polycyclic compounds. An example of the efficiency of this protocol is the two-step transformation of the acyclic precursor 409 into the tricyclic derivative 410. The cobalt-complexed acetal 409 was first transformed into the cyclooctyne derivative 411 via intramolecular reaction of the in situ generated propargyl cation 409a with the allylsilane moiety. Cyclooctyne 411 underwent smooth cycloaddition in the presence of carbon monoxide to give the target compound 410 with excellent stereoselectivity. 

All of these photoadducts obtained are polycyclic, and even polyfunctional molecules that have an a-cyclobutyl keto group. They can be used as very versatile starting materials for the synthesis of complex molecules. The [2-i-2]-photocycloaddition reaction constitutes a method of choice for creating a four-membered ring in polycycKc molecules. The photoreaction of a cyclopentenone unit with an alkene has recently been used in the synthesis of two natural products containing a cyclobutane unit — namely, sulcatine G and ( )-kelsoene (Scheme 14). ... 

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