Probing Host-Selective Phytotoxicity: Synthesis of Destruxin B and Several Natural Analogues
摘要:
The syntheses of the host-selective phytotoxin destruxin B [cyclo(beta Ala-Hmp-Pro-Ile-MeVal-MeAla), Hmp = (2R)-2-hydroxy-4-methylpentanoic acid], and the closely related natural analogues homodestruxin B (MeVal --> MeIle), desmethyldestruxin B (MeVal --> Val), hydroxydestruxin B (Hmp --> Dhmp, Dhmp = (2R)-2,4-dihydroxy-4-methylpentanoic acid), and hydroxyhomodestruxin B (MeVal --> MeIle, Hmp-Dhmp) are described. In each case, the MeAla-beta Ala linkage was formed by cyclization and the precursor linear hexadepsipeptides were formed by condensing two three-residue fragments. Radiolabeled samples of destruxin B, homodestruxin B, and hydroxydestruxin B were prepared by coupling [3-C-14]-beta -alanine to the appropriate pentadepsipeptide followed by cyclization. A noteworthy feature of the synthesis involves the novel use of a Boc-hydrazide protecting group on dipeptides with a C-terminal N-methylalanine residue to inhibit the otherwise facile dioxopiperazine formation during peptide coupling.
A chiral relay auxiliary for the synthesis of homochiral α-amino acids
作者:Steven D. Bull、Stephen G. Davies、Simon W. Epstein、Michael A. Leech、Jacqueline V. A. Ouzman
DOI:10.1039/a803124j
日期:——
A new chiral auxiliary (3S)-N,Nâ²-bis(p-methoxybenzyl)-3-isopropylpiperazine-2,5-dione 7 has been developed for the asymmetric synthesis of α-amino acids. The auxiliary 7 employs a novel chiral relay network based on non-stereogenic N-benzyl protecting groups which enhance the diastereoselectivity observed during alkylation of its C6 enolate 25.
Chiral relay auxiliary for the synthesis of enantiomerically pure α-amino acids
作者:Steven D. Bull、Stephen G. Davies、Simon W. Epstein、Jacqueline V. A. Ouzman
DOI:10.1039/a800407b
日期:——
Chiral auxiliary (3S)-N,Nâ²-bis(p-methoxybenzyl)-3-isopropylpiperazine-2,5-dione employs a chiral relay network based on non-stereogenic N-benzyl protecting groups to enhance diastereocontrol during enolate alkylation.
Probing Host-Selective Phytotoxicity: Synthesis of Destruxin B and Several Natural Analogues
作者:Dale E. Ward、Yuanzhu Gai、Ryszard Lazny、M. Soledade C. Pedras
DOI:10.1021/jo015953+
日期:2001.11.1
The syntheses of the host-selective phytotoxin destruxin B [cyclo(beta Ala-Hmp-Pro-Ile-MeVal-MeAla), Hmp = (2R)-2-hydroxy-4-methylpentanoic acid], and the closely related natural analogues homodestruxin B (MeVal --> MeIle), desmethyldestruxin B (MeVal --> Val), hydroxydestruxin B (Hmp --> Dhmp, Dhmp = (2R)-2,4-dihydroxy-4-methylpentanoic acid), and hydroxyhomodestruxin B (MeVal --> MeIle, Hmp-Dhmp) are described. In each case, the MeAla-beta Ala linkage was formed by cyclization and the precursor linear hexadepsipeptides were formed by condensing two three-residue fragments. Radiolabeled samples of destruxin B, homodestruxin B, and hydroxydestruxin B were prepared by coupling [3-C-14]-beta -alanine to the appropriate pentadepsipeptide followed by cyclization. A noteworthy feature of the synthesis involves the novel use of a Boc-hydrazide protecting group on dipeptides with a C-terminal N-methylalanine residue to inhibit the otherwise facile dioxopiperazine formation during peptide coupling.