TY - JOUR
T1 - Seven More Microcystins from Homer Lake Cells
T2 - Application of the General Method for Structure Assignment of Peptides Containing α, β-Dehydroamino Acid Unit(s)
AU - Namikoshi, Michio
AU - Sun, Furong
AU - Choi, Byoung Wook
AU - Rinehart, Kenneth L.
AU - Carmichael, Wayne W.
AU - Evans, William R.
AU - Beasley, Val R.
PY - 1995/6/1
Y1 - 1995/6/1
N2 - Larger scale isolation of microcystins, cyclic heptapeptide hepatotoxins, from a water bloom of Microcystis spp. collected from Homer Lake (Illinois) gave the previously reported 1-5, additional quantities of [L-MeSer7]microcystin-LR (6), and microcystin-(H4)YR [8, (H4)Y = 1;2;3;4′-tetrahydrotyrosine], which were previously isolated in insufficient amounts to complete the structure assignment, and seven more microcystins, 9-15. A general method for assigning the structures of cyclic peptides containing α, β-unsaturated amino acid unit(s) developed with nodularin, a cyclic pentapeptide hepatotoxin, was applied to confirm the previously assigned structures of 1-5 and to assign the structures of [D-Asp3]microcystin-LR (9) and the new microcystin-HilR (10, Hil = homoisoleucine). The method consists of linearization of a cyclic molecule by a one-pot reaction sequence (ozonolysis followed by NaBH4 reduction) and tandem FABMS (FABMS/CID/MS) analysis of the product (linear peptide). A new microcystin, 11, was assigned the structure [L-MeLan7]-microcystin-LR (MeLan = N-methyllanthionine) and synthesized from 1 and L-Cys. Four linear peptides 12-15, which are reasonable biogenetic precursors of the cyclic compounds, were also assigned structures based on their FABMS/CID/MS data.
AB - Larger scale isolation of microcystins, cyclic heptapeptide hepatotoxins, from a water bloom of Microcystis spp. collected from Homer Lake (Illinois) gave the previously reported 1-5, additional quantities of [L-MeSer7]microcystin-LR (6), and microcystin-(H4)YR [8, (H4)Y = 1;2;3;4′-tetrahydrotyrosine], which were previously isolated in insufficient amounts to complete the structure assignment, and seven more microcystins, 9-15. A general method for assigning the structures of cyclic peptides containing α, β-unsaturated amino acid unit(s) developed with nodularin, a cyclic pentapeptide hepatotoxin, was applied to confirm the previously assigned structures of 1-5 and to assign the structures of [D-Asp3]microcystin-LR (9) and the new microcystin-HilR (10, Hil = homoisoleucine). The method consists of linearization of a cyclic molecule by a one-pot reaction sequence (ozonolysis followed by NaBH4 reduction) and tandem FABMS (FABMS/CID/MS) analysis of the product (linear peptide). A new microcystin, 11, was assigned the structure [L-MeLan7]-microcystin-LR (MeLan = N-methyllanthionine) and synthesized from 1 and L-Cys. Four linear peptides 12-15, which are reasonable biogenetic precursors of the cyclic compounds, were also assigned structures based on their FABMS/CID/MS data.
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U2 - 10.1021/jo00117a017
DO - 10.1021/jo00117a017
M3 - Article
AN - SCOPUS:0029037188
SN - 0022-3263
VL - 60
SP - 3671
EP - 3679
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
IS - 12
ER -