An Unexpected Formation of a 14-Membered Cyclodepsipeptide

The treatment of diluted solutions of the hydroxy diamides 6a and 6b in toluene with HCl gas at 100° gave the dimeric, 14-membered cyclodepsipeptide 10 in up to 72% yield (Scheme 3). The same product was formed from the linear dimer of 6b, the depsipeptide 11, under the same conditions (cf. Scheme 4). All attempts to prepare the cyclic seven-membered monomer 9, starting with different precursors and using different lactonization methods failed, and 10 was the only product which was isolated (cf. Scheme 6). For example, the reaction of the ester 20 with NaH in toluene at 80° led exclusively to the cyclodimer 10. On the other hand, the base-catalyzed cyclization of the hydroxy diester 22, which is the ’O-analogue’ of 20, yielded neither the sevenmembered dilactone, nor the 14membered tetralactone, but only the known trimer 23 and tetramer 24 of 2,2dimethylpropano-3-lactone (cf. Scheme 7). DOI: https://doi.org/10.1002/hlca.200390262 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-80019 Accepted Version Originally published at: Iliev, Boyan; Linden, Anthony; Heimgartner, Heinz (2003). An unexpected formation of a 14-membered Cyclodepsipeptide. Helvetica Chimica Acta, 86(9):3215-3234. DOI: https://doi.org/10.1002/hlca.200390262 Prof. Dr. H. Heimgartner Tel.: 01/635 42 82 Fax : 01/635 68 36 e-mail: [email protected] An Unexpected Formation of a 14-Membered Cyclodepsipeptide by Boyan Iliev, Anthony Linden, and Heinz Heimgartner Organisch-chemisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057