“…Similarly, the cis isomer (5 S ,10b S )- 7a , the major adduct from the Pictet−Spengler cyclization, was converted to the methylselenyl ester (5 S ,10b S )- 12 as shown in Scheme . As with the regioisomer (5 S ,10b R )- 11 , the radical decarboxylation protocol transformed (5 S ,10b S )- 12 to the unnatural antipode of crispine A [( S )-(−)- 1 ] , in 39% isolated yield for the two-step process. The alkaloid enantiomer ( S )- 1 was found to rotate polarized light in an equal but opposite manner to ( R )- 1 and was also shown to be a single isomer by chiral HPLC analysis (see Supporting Information).…”