Methyl diformylacetate

Similarly, methyl diformylacetate, a /(-tricarbonyl compound, is almost totally enolized towards the aldehyde and reacts smoothly with alkenes to give a hemiacetal structure 7 present in many of the iridoid glucosides113-116. 

Methyl diformyl acetate can be prepared from ketene and trimethyl orthoformate, or methyl proplolate and methanol, via formylation of the methyl 3,3-diraethoxypropanoate intermediate (eq. 1). The present procedure is better because it avoids the tedious preparation of ketene, affords a superior yield, or is much cheaper than the other two methods. A fourth method for its preparation (eq. 2) should permit the preparation of any ester of diformylacetic acid that is stable to Birch reduction and ozonolysis conditions. However, this method is not convenient for use above a 0.1-mole scale, nor recommended for reasons of safety because of the amount of an O2/O3 mixture needed at larger scales. 

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