The specific aims of this grant include two total syntheses which are based on aldol chemistry developed in these laboratories three years ago. This methodology utilizes the chemistry of enolate systems arising from vinylogous urethanes. The first of these synthetic targets is the macrolide antibiotic rosaramycin (1), a molecular system of considerable biological interest. Our synthetic effort on this molecule is in its third year. The progress report and first part of the experimental design and methods section of this proposal will discuss the current status of this problem and our intended future efforts on it, respectively. The second part of this proposal involves a construction of the seco-acid of erythromycin (2). In this section, we will propose a detailed study of the methodology we intend to employ for the synthesis along with a description of the synthetic route itself.