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41.
[reaction: see text] A novel approach to the formation of the unusual pyrone-containing ring systems as found in polypropionate metabolites from the Tridachia family of marine molluscs has been developed. This approach includes an intramolecular cyclization of a beta-keto acid onto a cyclohexenone ring to afford a fused, bicyclic pyrone. 相似文献
42.
[reaction: see text] The solid-phase assembly of heterocyclic amino acids enabled the total synthesis of numerous diastereoisomers of tenuecyclamides A-D, establishing or correcting the stereochemistry of each natural product. This strategy provides a very efficient route to synthesize thiazole- and oxazole-containing macrolactams from heterocyclic amino acids that are readily prepared from Fmoc-alpha-amino acids. This methodology appears to be broadly applicable to the synthesis of natural product libraries incorporating unnatural heterocyclic amino acid residues for the purpose of drug discovery. 相似文献
43.
Harding LP Jeffery JC Riis-Johannessen T Rice CR Zeng Z 《Dalton transactions (Cambridge, England : 2003)》2004,(16):2396-2397
The amide-substituted unsymmetrical ligand L(1) upon coordination to Co(2+) forms the dinuclear triple helicate [Co(2)(L(1))(3)](4+) which exists as both possible C(1) and C(3) symmetric geometric isomers in solution, however, upon addition of nitrate ions, the formation of an anion binding cavity is favoured and hence the sole product is the C(3) symmetric isomer in which all three amide substituents are hydrogen bonded to the nitrate anion. 相似文献
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Donald W. Combs Jeffery B. Press Dennis Mulvey Yolanda Gray-Nunez Stanley C. Bell 《Journal of heterocyclic chemistry》1986,23(4):1263-1264
A ring contraction of 1,4-benzodiazepin-2-one to 2-chloromethylquinazoline in phosphoryl chloride is described. The intermediacy of an aziridinoquinazoline is proposed. 相似文献
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Saven JG 《Current Opinion in Colloid & Interface Science》2010,15(1-2):13-17
Computational protein design facilitates the continued development of methods for the design of biomolecular structure, sequence and function. Recent applications include the design of novel protein sequences and structures, proteins incorporating nonbiological components, protein assemblies, soluble variants of membrane proteins, and proteins that modulate membrane function. 相似文献
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Alonso M Alvarez MA García ME Ruiz MA Hamidov H Jeffery JC 《Inorganic chemistry》2010,49(24):11595-11605
The anionic oxophosphinidene complexes (H-DBU)[MCp{P(O)R*}(CO)(2)] (M = Mo, W; R* = 2,4,6-C(6)H(2)(t)Bu(3); Cp = η(5)-C(5)H(5), DBU = 1,8-diazabicyclo [5.4.0] undec-7-ene) displayed multisite reactivity when faced with different electrophilic reagents. The reactions with the group 14 organochloride compounds ER(4-x)Cl(x) (E = Si, Ge, Sn, Pb) led to either phosphide-like, oxophosphinidene-bridged derivatives [MCp{P(OE')R*}(CO)(2)] (E' = SiMe(3), SiPh(3), GePh(3), GeMe(2)Cl) or to terminal oxophosphinidene complexes [MCp{P(O)R*}(CO)(2)(E')] (E' = SnPh(3), SnPh(2)Cl, PbPh(3); Mo-Pb = 2.8845(4) ? for the MoPb compound). A particular situation was found in the reaction with SnMe(3)Cl, this giving a product existing in both tautomeric forms, with the phosphide-like complex [MCp{P(OSnMe(3))R*}(CO)(2)] prevailing at room temperature and the tautomer [MCp{P(O)R*}(CO)(2)(SnMe(3))] being the unique species present below 203 K in dichloromethane solution. The title anions also showed a multisite behavior when reacting with transition-metal based electrophiles. Thus, the reactions with the complexes [M'Cp(2)Cl(2)] (M' = Ti, Zr) gave phosphide-like derivatives [MCp{P(OM')R*}(CO)(2)] (M = Mo, M' = TiCp(2)Cl, ZrCp(2)Cl; M = W, M' = ZrCp(2)Cl), displaying a bridging κ(1),κ(1)-P,O- oxophosphinidene ligand connecting MCp(CO)(2) and M'Cp(2)Cl metal fragments (W-P = 2.233(1) ?, O-Zr = 2.016(4) ? for the WZr compound]. In contrast, the reactions with the complex [AuCl{P(p-tol)(3)}] gave the metal-metal bonded derivatives trans-[MCp{P(O)R*}(CO)(2){AuP(p-tol)(3)}] (M = Mo, W; Mo-Au = 2.7071(7) ?). From all the above results it was concluded that the terminal oxophosphinidene complexes are preferentially formed under conditions of orbital control, while charge-controlled reactions tend to give derivatives with the electrophilic fragment bound to the oxygen atom of the oxophosphinidene ligand (phosphide-like, oxophosphinidene-bridged derivatives). 相似文献