Synthesis of the Angiotensin-Converting Enzyme Inhibitors (−)-A58365A and (−)-A58365B from a Common Intermediate

(−)-A58365A (<b>1</b>) and (−)-A58365B (<b>2</b>), which are inhibitors of angiotensin-converting enzyme, were synthesized from the subunits <b>9</b> and <b>10</b>. These were coupled, and the resulting individual amides <b>17a</b>,<b>b</b> were converted by ozonolysis into aldehydes <b>18a</b>,<b>b</b>, which underwent cyclodehydration to the enamides <b>19a</b>,<b>b</b>. Treatment with a stannane served to generate the vinyl stannanes <b>20a</b>,<b>b</b>, from which ketones <b>22a</b>,<b>b</b> were produced by protodestannylation and ozonolysis. Base treatment and hydrogenolysis then afforded (−)-A58365A (<b>1</b>). The intermediates <b>17a</b>,<b>b</b> were also converted into aldehydes <b>26a</b>,<b>b</b> by hydroboration and oxidation, and a similar sequence to that used for (−)-A58365A was then applied in order to complete the first enantiospecific synthesis of the congener, (−)-A58365B (<b>2</b>).