As shown above in Scheme 7, the remaining tetralone was then converted to the methyl ester (9). Using a procedure from Gregory, G. B. and Johnson, A. L, JOC, 1990, 55, 1479, the tetralone methyl ester (9) was converted, first, to the cyanohydrin by treatment with trimethylsilylcyanide and zinc iodide and then, via the in situ dehydration with phosphorous oxychloride in pyridine, to the methyl 8-cyano-5,6-dihydro-2-naphthoate (11). This naphthoate was divided into two portions and some was subjected to hydrogenolysis, N-BOC-protection and saponification to give N-(BOC)-8-aminomethyl-5,6,7,8-tetrahydro-2-naphthoic acid (12) as an intermediate for incorporation into the cyclic peptide.
