- Efficient method for the deprotection of tert-butyldimethylsilyl ethers with TiCl4-Lewis base complexes: Application to the synthesis of 1β-methylcarbapenems
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TiCl4-Lewis base (AcOEt, CH3NO2) complexes smoothly deprotected tert-butyldimethylsilyl (TBDMS) ethers. The reaction velocity with these complexes, which seemed less reactive due to the influence of Lewis bases, was considerably greater than that with TiCl4 alone. Selective desilylations between aliphatic and aromatic TBDMS ethers (1 and 5), between 1 and benzyl, allyl, tosyl, methoxyphenyl, and chloroacetyl ethers (13, 14, 15, 16, and 17), and between TBDMS and TBDPS ethers (18 and 19) were successfully performed. Desilylation of TBDMS-aldol, acyloin, and β-lactam analogues 9-12 proceeded smoothly due to anchimeric assistance by the neighboring carbonyl groups. The present method was successfully applied to the practical synthesis of 1β-methylcarbapenems 20a′-f′.
- Iida, Akira,Okazaki, Hiroki,Misaki, Tomonori,Sunagawa, Makoto,Sasaki, Akira,Tanabe, Yoo
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p. 5380 - 5383
(2007/10/03)
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- Simple and Condensed β-Lactams. Part 23. Synthesis of Some Compounds Related to the Monobactams, Carrying Non-Acylamino Substituents in Position 3 and Various Heterocyclyl or Heterocyclylmethyl Substituents in Position 4 of the β-Lactams Ring
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Racemic monobactam analogues 8a-8c, 8e-8g, 8n, 27, 44k-44m, 48c and 51d, carrying hydrogen or non-acylamino substituents in position 3, and 2-substituted thiazol-4-yl, 2-substituted thiazol-4-ylmethyl, 4-substituted yhiazol-2-ylmethyl, 2-benzyltetrazol-5-ylmethyl or 5-methoxyisoxazol-3-ylmethyl substituents in position 4 of the β-lactam ring, as well as the reversed monobactam 35 were synthesised.None of the compounds synthesised exhibited any microbiological activities.Base catalyzed rearrangement of a 4-cyanomethylazetidin-2-one (39j) into a 6-aminopyridin-2(1H)-one (40) and acid catalyzed rearrangements, with elimination of the lactam nitrogen atoms, of two 4-(thiazol-2-ylmethyl)azetidin-2-ones (44a, 44b) into a thiazolopyridinone (47) were observed.
- Fetter, Jozsef,Bertha, Ferenc,Czuppon, Tibor,Kajtar-Peredy, Maria,Lempert, Karoly
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p. 2738 - 2789
(2007/10/03)
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- A PRACTICAL SYNTHESIS OF (+/-)-THIENAMYCIN
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An efficient and operationally simply synthesis of (+/-)-thienamycin is described.
- Melillo, D.G.,Shinkai, I.,Liu, T.,Ryan, K.,Sletzinger, M.
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p. 2783 - 2786
(2007/10/02)
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