Lehmann-Traube-synthesis

Pyrocin may also be synthesized in a more classical manner by the Lehmann-Traube synthesis, which comprises the opening of epoxides 38 with malonic esters to give butyrolactons with usually good yields [56], (Reaction scheme 27). 

Therefore there are several strategies to obtain permethric acid by the synthesis of such butyrolactones. The Lehmann-Traube synthesis of the epoxide 129 and malonic ester (Reaction scheme 82) [214, 215] yields an product 128, isomeric to 102 in the preceding Reaction schemes 64, 79, 80, 81. 

The application of the Lehmann-Traube synthesis [433] (Reaction scheme 150) yields predominantly the trans-isomer, with substantial amounts of the E-isomer. 

In a short and elegant synthesis, pyrocine is accessible via the Lehmann-Traube method, in which the monoepoxide of 2,5-dimethylhexa-2,4-diene is reacted with a malonic ester. After hydrolysis and decarboxylation, pyrocine is obtained, which, like isopyrocine, can be converted into chrysanthemic acid by thionyl chloride and base-induced 1,3-cydoelimination. [88]... 

The a-bromo-4-chloro derivative described by Traube and Lehmann (79 798) was used in the original synthesis. 

---

See also in sourсe #XX -- [ , , ]

---