- Lipase-catalyzed site-selective deacetylation of sterically hindered naphthohydroquinone diacetate and its application to the synthesis of a heterocyclic natural product
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Lipase-catalyzed site-selective deacetylation of 2,5-dimethylnaphthalene-l,4-diol diacetate was examined. With Candida antarctica lipase B, the suppressing effect of a methyl substituent at the peri-position of the a-naphthyl ester over that at the ortho-position was significant. This site-selectivity was in contrast to that of chemical hydrolysis reported to date. From the resulting monoacetate, mansonone F, a physiologically active heterocyclic orthoquinone, was synthesized in 38% yield in as few as three steps.
- Hanaya, Kengo,Hashimoto, Riichi,Higashibayashi, Shuhei,Sakakura, Ayaka,Sugai, Takeshi
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p. 625 - 632
(2019/08/01)
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- A Platform of Regioselective Methodologies to Access Polysubstituted 2-Methyl-1,4-naphthoquinone Derivatives: Scope and Limitations
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A platform of synthetic methodologies has been established to access a focused library of polysubstituted 3-benzylmenadione derivatives functionalized on the aromatic ring of the naphthoquinone core. Two main routes were explored: 1) The naphthol route, starting from either an α-tetralone or a propiophenone, and 2) the regioselective Diels-Alder reaction, starting from various dienes and two 2-bromo-5(or 6)-methyl-1,4-benzoquinones. 6-Substituted 2-methylnaphthols were synthesized by using a xanthate-mediated free-radical addition/cyclization sequence for the construction of the 6-substituted menadione subunit. Furthermore, an efficient and simple new pathway that allows the formation of 6- or 7-substituted 3-(substituted-benzyl)menadione regioisomers from a common commercial scaffold has also been developed by the naphthol route, advantageous with regard to step economy. Our synthetic methodologies exemplified by 34 compounds have allowed structure-activity relationships to be deduced for use as the basis for the development of new antimalarial redox-active polysubstituted benzylmenadione derivatives.
- Rodo, Elena Cesar,Feng, Liwen,Jida, Mouhamad,Ehrhardt, Katharina,Bielitza, Max,Boilevin, Jérémy,Lanzer, Michael,Williams, David Lee,Lanfranchi, Don Antoine,Davioud-Charvet, Elisabeth
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p. 1982 - 1993
(2016/04/26)
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- TOTAL SYNTHESIS OF REDOX-ACTIVE 1.4-NAPHTHOQUINONES AND THEIR METABOLITES AND THEIR THERAPEUTIC USE AS ANTIMALARIAL AND SCHISTOMICIDAL AGENTS
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Naphthoquinones, azanaphthoquinones and benxanthones, their process of synthesis and their use as antimalarial or antischistosomal agents.
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Page/Page column 84-85
(2012/10/18)
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- Antimony pentachloride catalyzed Diels-Alder reactions: Improved regioselectivity in the synthesis of dialkyl naphthoquinones
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Improved regioselectivity in catalyzed Diels-Alder (DA) cycloadditions between non-symmetrical benzoquinones and mono-substituted butadienes is achieved by use of SbCl5. After oxidation, good yields of dialkylnaphthoquinones are obtained. The g
- Nunes, Ruth Leandro,Bieber, Lothar Wilhelm
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p. 219 - 221
(2007/10/03)
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- Reactions of semiquinones in aqueous solution. A comparison of the one electron reduction of kalafungin and analogues with other semiquinones using pulse radiolysis
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The radical anions of the pyranonaphthoquinone antibiotic kalafungin 1 and analogues have been studied in aqueous solution by pulse radiolysis using transient absorption spectrophotometry. Radical absorption spectra were similar regardless of the nature of the substituent at C-5 or C-7 and the decay followed second-order kinetics showing any potential first-order ring opening was too slow to compete with bimolecular disproportionation at the concentration of radicals produced by pulse radiolysis. Spectral studies using steady-state radiolysis confirmed the absence of ring opening. The pKa of each of the semiquinones of compounds 1-5 were determined and whereas replacing a hydrogen at C-7 by a methoxy, 2 and 4, raises the pKa by 2.5-2.9 units demonstrating a significant substituent effect, no such increase occurs for OH, 1. This and the fact that kalafungin, 1, has the most positive one-electron reduction potential E(1), -63 ± 10 mV in neutral solution, is attributed to H-bonding between the 7-OH and the oxygen of the semiquinone, with the H-bonding effectively nullifying the substituent effect. The presence of an OH on C-5 has a much less significant effect on the E(1) and pKa values. Comparison of kinetics and products in systems with and without tert-butanol brings into question a report that 2-(methoxymethyl)benzo1,4-quinone and 2-(phenoxymethyl)benzo-1,4-quinone undergo dissociation on one-electron reduction.
- Anderson, Robert F.,Brimble, Margaret A.,Nairn, Michael R.,Packer, John E.
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p. 475 - 479
(2007/10/03)
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- Synthesis and redox potentials of methylated vitamin K derivatives
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We report the synthesis of derivatives of vitamin K3 as well as of vitamins K1 and K2 containing a different number of methyl groups in various positions in order to reduce their redox potentials and to change systematically their steric features. The long aliphatic chain of vitamins K1 and K2 is simulated by an undecyl chain or a methyl group, respectively. The redox potentials of the first reduction step were measured by cyclic voltammetry in DMF. These compounds are relevant for studies of the structure-function relationship of vitamin K dependent enzymes and the investigation of electron transfer reactions in photosynthetic reaction centers.
- Schmid, Ralf,Goebel, Friederike,Warnecke, Andre,Labahn, Andreas
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p. 1199 - 1202
(2007/10/03)
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- Naphthalene anti-psoriatic agents
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Psoriasis in mammals is relieved by topically administering naphthalenes of the formula: STR1 wherein: R1 is lower alkoxy or optionally substituted phenoxy; R2 is hydrogen, lower alkyl, optionally substituted phenyl or optionally substituted phenyl-lower-alkyl; R3 is hydrogen, lower alkyl, lower alkoxy, halo, optionally substituted phenyl, optionally substituted phenyl-lower-alkyl or optionally substituted phenyl-lower-alkoxy, and m is 1 or 2; X and Y are different and are selected from the group consisting of hydrogen, R4 and -C(O)W, wherein W is alkyl of one to seven carbon atoms, optionally substituted phenyl or optionally substituted benzyl; and R4 is lower alkyl or optionally substituted phenyl-lower-alkyl.
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- METHOD FOR TREATING DISEASE STATES IN MAMMALS WITH NAPHTHALENE LIPOXYGENASE-INHIBITTNG AGENTS
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Psoriasis in mammals is relieved by topically administering naphthalenes of the formula: wherein: R1 is lower alkoxy or optionally substituted phenoxy, R2 is the same as R1, or R2 is hydrogen, lower alkyl, optionally substituted phenyl or optionally substituted phenylalkyl, R3 is hydrogen, lower alkyl, lower alkoxy, halo, optionally substituted phenyl, optionally substituted phenyl-lower-alkyl or optionally substituted phenyl-lower-alkoxy, and m is 1 or 2; both X groups are the same and X is either -C(O)OR4 or -C(O)NR5R6 , wherein R4 is alkyl, phenyl or benzyl optionally substituted with one or two lower alkyl groups, lower alkoxy groups or halo; and R5 and R6 are independently hydrogen, lower alkyl, cycloalkyl or phenyl optionally substituted with one or two lower alkyl groups, lower alkoxy groups or halo. The compounds of this invention are also useful for the treatment of disease-states caused by lipoxygenase activity in mammals, particularly 5-lipoxygenase activity, when administered systemically.
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- Naphthalene lipoxygenase-inhibiting agents
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Psoriasis in mammals is relieved by topically administering naphthalenes of the formula: STR1 wherein: R1 is lower alkoxy or optionally substituted phenoxy; R2 is hydrogen, lower alkyl, optionally substituted phenyl or optionally substituted phenylalkyl; R3 is hydrogen, lower alkyl, lower alkoxy, halo, optionally substituted phenyl, optionally substituted phenyl-lower-alkyl or optionally substituted phenyl-lower-alkoxy, and m is 1 or 2; X and Y are different and are either R4 or --C(O)W wherein R4 is lower alkyl or optionally substituted phenyl-lower-alkyl; W is --OR5 or --NR6 R7, wherein R5 is alkyl, optionally substituted phenyl or optionally substituted benzyl; and R6 and R7 are independently hydrogen, lower alkyl, cycloalkyl or optionally substituted phenyl. The compounds of this invention are also useful for the treatment of disease-states caused by lipoxygenase activity in mammals, particularly 5-lipoxygenase activity, when administered systemically.
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- Naphthalene anti-psoriatic agents
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Psoriasis in mammals is relieved by topically administering naphthalenes of the formula: STR1 wherein: R1 is lower alkoxy or optionally substituted phenoxy; R2 is hydrogen, lower alkyl, optionally substituted phenyl or optionally substituted phenylalkyl; R3 is hydrogen, lower alkyl, lower alkoxy, halo, optionally substituted phenyl, optionally substituted phenyl-lower-alkyl or optionally substituted phenyl-lower-alkoxy, and m is 1 or 2; X and Y are different and are either R4 or --C(O)W wherein R4 is lower alkyl or optionally substituted phenyl-lower-alkyl; W is --OR5 or --NR6 R7, wherein R5 is alkyl, optionally substituted phenyl or optionally substituted benzyl; and R6 and R7 are independently hydrogen, lower alkyl, cycloalkyl or optionally substituted phenyl.
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- Catalytic Asymmetric Induction in Oxidation Reactions. Synthesis of Optically Active Epoxynaphthoquinones
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Optically active 2,3-epoxides of a variety of substituted 1,4-naphthoquinones have been prepared in an asymmetric synthesis.Enantiomeric excess of up to 45percent were realized.Some data could be obtained concerning the influence of substituents on the en
- Pluim, Henk,Wynberg, Hans
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p. 2498 - 2502
(2007/10/02)
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