rekest-b


	The idea of this program was to improve SAS which was unable to generate rearrangements or fragmentation. For example if we consider the synthesis of Longifolene by Oppolzer (J. Am. Chem. Soc., 1978, 100, 2583) in which the key step involves an intramolecular de Mayo reaction ( (2+2 ) then retro aldol) :


	With SAS the following precursor could eventually suggest this idea :


	So we decided to adapt SOS where we coded “pseudo reactions” which add and / or delete bonds in the skeleton of the target, such as :


	Reactions which delete bonds :


	Reactions which add bonds :


	Reaction which adds and deletes two bonds :


	For Longifolene framework, adding one bond generates several solutions, among them :


	Which suggests the attack of a carbene on a double bond then oppening of the cyclopropane ring :


	This approach is known : Fallis et al. Canad. J. Chem. 1984, 62, 1709 and 1717.


	It suggests a similar strategy, which is new :


	Addition of one bond :


	Addition and deletion of two bonds :


	Could suggest the synthesis of Longifolene by Oppolzer.


	The main drawback is that it generates a great number of solutions. The search for the key step of a synthesis was improved with CONAN and HOLOWin programs.

Paper :

26 - REKEST : a computer program to REsearch for the KEy STep of a synthesis
R. Barone and M. Chanon
Chimia, 1986, 12, 436-439.


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