- Asymmetric synthesis of (2S,3S)-3-Me-glutamine and (R)-allo-threonine derivatives proper for solid-phase peptide coupling
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Practical new routes for preparation of (2S,3S)-3-Me-glutamine and (R)-allo-threonine derivatives, the key structural components of cytotoxic marine peptides callipeltin O and Q, suitable for the Fmoc-SPPS, were developed. (2S,3S)-Fmoc-3-Me-Gln(Xan)-OH was synthesized via Michael addition reactions of Ni (II) complex of chiral Gly-Schiff base; while Fmoc-(R)-allo-Thr-OH was prepared using chiral Ni (II) complex-assisted α-epimerization methodology, starting form (S)-Thr(tBu)-OH.
- Tokairin, Yoshinori,Soloshonok, Vadim A.,Moriwaki, Hiroki,Konno, Hiroyuki
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- Synthetic studies on callipeltins: Stereoselective syntheses of (3S,4R)-3,4-dimethyl-L-pyroglutamic acid and fmoc-D-allothreonine from serine derivatives
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The non-proteinogenic amino acids contained in callipeltins, (3S, 4R)-3, 4-dimefhyl-L-pyroglutamic acid and D-allothreonine, were synthesized from D- or L-serine. The stereoselective synthesis of two methyl groups of (3S, 4R)-3, 4-dimethyl-L-pyroglutamic acid was accomplished by diastereoselective hydrogenation and alkylation. Kinetic epimerization of the C-4 methyl substituent followed by Boc-deprotection with 10% TFA gave the desired (3S, 4R)-3, 4-dimethyl-L-pyroglutamic acid as a single isomer.
- Konno, Hiroyuki,Takebayashi, Yoko,Nosaka, Kazuto,Akaji, Kenichi
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- Improved synthesis of d-allothreonine derivatives from l-threonine
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The improved synthesis of protected d-allothreonine derivatives [Fmoc-d-alloThr(tBu)-OH (1) and Fmoc-d-alloThr-OtBu (2)] is described. The epimerization of cheap l-threonine (l-Thr) (3) with catalytic salicylaldehyde afforded a mixture of l-Thr (3) and d-alloThr (4) and separation of ammonium salt gave d-alloThr (4) in 96% de. The chemoselective deprotection of tert-butyl ether or tert-butyl ester of Fmoc-d-alloThr(tBu)-O tBu (5) easily succeeded in converting Fmoc-d-alloThr( tBu)-OH (1) or Fmoc-d-alloThr-OtBu (2), respectively.
- Kikuchi, Mari,Konno, Hiroyuki
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- Solid phase total synthesis of callipeltin e isolated from marine sponge Latrunculia sp.
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Solid phase total synthesis of callipeltin E (1), truncated linear peptide isolated from marine sponge, Latrunculia sp. was achieved. Our strategy based on traditional Fmoc-SPPS was in common use TFA-treatment final deprotection to reach callipeltin E (1) contained acid-sensitive βMeOTyr.
- Kikuchi, Mari,Nosaka, Kazuto,Akaji, Kenichi,Konno, Hiroyuki
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p. 3872 - 3875
(2011/08/09)
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- Synthesis of Nα-(9-Fluorenylmethoxycarbonyl)-Allothreonine t-Butyl Ether via Threonine Oxazolines
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New procedures for the preparation of allothreonine, suitably protected for solid phase peptide synthesis, were developed.Stereochemical inversion in the side chain of threonine via thionyl chloride-induced oxazoline cyclisation and subsequent hydrolysis, followed by protection of the allothreonine amino and hydroxyl functions provided Fmoc-D-alloThr(But)-OH from benzoyl-D-threonine phenacyl ester in only five steps.Alternatively, it was shown that temporary carboxyl protection for introduction of the t-butyl ether group can be circumvented by direct selective ester acidolysis from Fmoc-Thr(But)-OBut.
- Fischer, Peter M.,Sandosham, Jessie
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p. 5409 - 5412
(2007/10/02)
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