Fragmentation of Linear Peptide Alkaloids

These alkaloids, due to their open structure, fragment in a special way. 

R = Basic end amino acid residue r1 = Sty-bound amino acid residu r2 = oh or H 

They exhibit fragments a-1, which are displayed in Fig. 21 (60, 61). We note the following i) The celenamides are marine natural products of sponge origin and usually bear a Br atom in R side chain ii) some of the fragments, due to the presence of Br, exhibit two isotope peaks which 

This alkaloid contains a unique structure. It is comprised of five units, four of them being attached to one side of the aminophenol, the fifth unit. The ring-bound amino acid bears an additional basic terminal amino acid. According to Marchand et al. (62) the fragments that are encountered are i (m/z=135), a and o (mlz = S6 and 58 respectively). They originate from one basic terminal amino acid (N-Me-L-Val) in accord with the fragmentation behaviour of 4(14)-frangulanine-type cyclopeptide alkaloids. 

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