In the preceding papers (1) successful syntheses for representative /3-substituted " ^-butenolides have been described and evidence has been presented (2) which suggests that the natural cardiac aglycones are best represented by such a structure rather than by that of a ß i'-butenolide. Concurrently with these investigations we have studied other possible methods by which the ß i'-butenolides might be prepared. These projected syntheses involved, for the most part, the preparation of 0-substituted-/9-aldehydopropionic acids and subsequent ring closure through the enolic form. It now seems probable as a result of our own observations (2), as well as earlier ones of others (3,4,5), that ring closure of such an aldehyde acid to a ß •i'-unsaturated lactone is at best exceedingly difficult if not impossible. Although the desired /9-aldehydopropionic acids are now readily available (1, 2) we wish to present the results of the exploration of a number of suggested syntheses of these substances.The most direct route to such aldehydo acids appeared to be based on the work of Perkin and Sprankling (6) who prepared /9-aldehydopropionic acid by condensation of bromoacetal with sodio malonic ester and decarboxylation of the product. The logical extension of this synthesis would involve a similar condensation of the acetal of any appropriate a-bromoaldehyde. In an exploratory investigation we have attempted the con-