the isolation , elucidation and synthetic replication of novel pentapeptidemides and esters are described . the compounds have the general structure ## str1 ## in which r 1 and r 2 are selected as shown below : ## str2 ## r . sub . 1 = ch . sub . 3 ; r . sub . 2 =-- o -- ch . sub . 2 ch . sub . 2 ch . sub . 2 ch . sub . 2 ch 3 16a ) r . sub . 1 = ch . sub . 3 ; r . sub . 2 =-- o -- ch . sub . 2 ch . sub . 2 ch . sub . 2 ch . sub . 2 ch 2 ch 2 ch 2 ch 3 16b ) r . sub . 1 = ch . sub . 3 ; r . sub . 2 =-- nh -- ch . sub . 2 ch . sub . 2 ch . sub . 2 ch . sub . 2 ch 2 ch 3 16c )