Synthesis of the aphin-related (±)-7,9-dideoxyquinone A and (±)-7,9-dideoxyquinone A′

Chorn, Trevor A.; Giles, Robin G. F.; Green, Ivan R.; Mitchell, Peter R. K.

doi:10.1039/p19830001249

Cited by 20 publications

(11 citation statements)

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“…This outcome is in sharp contrast to the alternative oxidative cyclisation mentioned above (Scheme 2) which is achieved for the isomeric conjugated propenyl substituent. 13 The use of ceric ammonium nitrate (four equivalents) gave the same quinone 13, but in reduced yield (72%), presumably as a consequence of oxidative decomposition of this product. The quinone 13 was then treated with bis(acetonitrile)dichloropalladium(II) to form the benzisochromenequinone 14 in reasonable yield (Scheme 4).…”

Section: Methodsmentioning

confidence: 99%

“…Nevertheless, two elegant short assemblies of these compounds from 2-(1'-hydroxyethyl)-1,4-naphthoquinone have been reported recently, 10,11 and the former method extended to the assembly of the related benzisochromanequinones through stereoselective reduction. We have shown previously that 3-allyl-2-(1'-hydroxyethyl)-1,4-dimethoxynaphthalene 1 undergoes a completely diastereoselective base-induced cyclisation to afford solely the isomeric trans 1,3-dimethylnaphthopyran 2 in virtually quantitative yield, 12 and that the conjugated double bond structural isomer 3 of substrate 1 undergoes oxidative cyclisation with ceric ammonium nitrate (four equivalents) to yield directly the 7,9-dideoxy analogues 4 and 5 13 of the aphid insect pigment derivatives quinone A 6 and quinone A' 7.…”

Section: Introductionmentioning

confidence: 99%

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A model for the synthesis of naturally occurring benzisochromenequinones

Giles¹,

Green²,

Taylor³

2002

Arkivoc

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A model for the synthesis of naturally occurring benzisochromenequinones

Giles¹,

Green²,

Taylor³

2002

Arkivoc

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“…The fact that the coupling constants between 3-H and 4-H were small (1-1.5 Hz) in each case confirmed that, with the 3methyl equatorial, the hydroxy (or acetoxy) group was pseudoaxial. , 20 With the relative stereochemistry established at C-3 and C-4, it only remained to determine the configurations at C-1 and also whether the products were linear or angular naphthopyrans.…”

Section: Ohmentioning

confidence: 99%

“…The extract was washed with brine and the residue obtained upon work-up was chromatographed on alumina (eluent 15% ethyl acetate-light petroleum) to afford the (Z)-olefin 31 (15 mg, 82%) as an oil (Found: C, 59.3; H, 5.6. C,,H,,BrO, requires C, 59.2; H, 5.75%); v,a,(film)/cm-l 1615 and 1590 (W); & 1.36 [6 H, d, J 6.1, CH(CH),),], 1.80 (3 H, dd, J 7 and 1 .5, 3'-CH,), 3.90 and 3.95 (each 3 H, s, OCH,), 4.50 [sept., J6.1, CH(CH,),], 5.91 (1 H, dq, J 11.5 and 7,2'-H), 6.51 (1 H, d, J 1.5,6-H), 6.65 (1 H, dq, J 11.5 and 1.5, 1'-H), 6.72 (1 H, s, 3-H) and 7.29 (1 H, d, J 1.5, 8-H); m/z 366 (M', 42%), 364 (M', 42%), 324 (loo), 322 (loo), 285 (20) and 243 (80). 8-Brorno-2-hydroxymethyl-4-isopropoxy-5,7-dimethoxynaphthalene 27.-The acetate 25 (500 mg, 0.50 mmol) was dissolved in 1% (w/v) methanolic potassium hydroxide (105 mg, 1.88 mmol) and the solution stirred for 10 min at room temperature.…”

Section: Rel-( 1 R2s)-1 -( 1 -Bromo-4-isopropoxy-57-dimethoxynaphthal...mentioning

confidence: 99%

The stereoselective formation of naphtho[1,2-c]pyrans, angular analogues of the aphin-derived glucoside B, by an intramolecular version of the Mukaiyama reaction of 4-naphthyldioxolanes

Giles¹,

Green²,

Knight³

et al. 1994

J. Chem. Soc., Perkin Trans. 1

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“…132. 5 H,s,~-H),~.~I(IH,~,J~Hz,~-H),~.~~(I H, 3-Acetyl-1,5,7-frimethoxy-4-nuphthol( 14). -The acetate (12) (0.332 g) and boron trifluoride (4 ml) were heated as above.…”

Section: 5-dimethoxy-4-naphthol (9mentioning

confidence: 99%

The acetylation of naphthoquinones. The synthesis of 3-acetyl-5-methoxy- and 3-acetyl-5,7-dimethoxy-1,4-naphthoquinones

Chorn¹,

Giles²,

Green³

et al. 1984

J. Chem. Soc., Perkin Trans. 1

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The conversion of 5-methoxy-and 5,7-dimethoxy-1,4-naphthoquinones into their 3-acetyl derivatives is described. A key step is the Fries rearrangement of 1,5-dirnethoxy-4-acetoxynaphthalenes to the corresponding 3-acetyl-4-naphthols with boron trifluoride-diethyl ether. Alternative Fries rearrangement of I -acetoxy-4-hydroxy-5-methoxynaphthalenes gave the 3-acetylquinols, involving meta migration of the acetyl group. A convenient new synthesis of 2-acetyl-l,4-naphthoquinone is also reported.The naphtho[2,3-c]pyran ring system occurs not infrequently in Nature as derivatives of the 5,10-quinone. Examples are the eleutherins,' the nanaomycins,2 and the p r~t o a p h i n s .~ Certain analogues lacking oxygen(s) in the aromatic ring have been synthesised using 2-acetyl-1,4-naphthoquinone (1) as starting material; for example, 9-deoxykalafungin (4) and 7,9-dideoxyquinones A (5) and A' (6),' the latter being derivatives of the protoaphins. Preparation of the natural products themselves requires appropriate regiospecific aromatic oxygenation of 2-acetylnaphthoquinone. We describe here syntheses of 3-acetyl-5-methoxy-1,4-naphthoquinone (2) t and the corresponding 5,7-dimethoxy analogue (3),7 and are currently investigating the use of these in the formation of several naturally occurring quinones or their derivatives. In the course of this work, an unusual Fries rearrangement was established.to the product was supported inter alia by a sharp lowfield singlet at 6 13.46 in its 'H n.m.r. spectrum due to the strongly hydrogen bonded hydroxy group. Oxidation of this compound with ceric ammonium nitrate gave rise to the desired 3-acetyl-5-methoxy-1,4-naphthoquinone (2) in an overall yield of 67% from (7). 0 ( 7 ) R = H ( 8 ) R = OMe M e 0 OH R OMe ( 9 ) R = H (10) R = OMe ( 4 ) ( 1 ) R ' = R~= H ( 2 ) R'=OMe, Rz:H ( 3) R'= RZ = OMe 0 Me ( 5 ) R' = O H , R~ = H ( 6 ) R 1 = H , R 2 = O H Results and DiscussionJuglone methyl ether (7) was reductively monomethylated at the less hindered oxygen to give the naphthol (9) using sodium dithionite followed by treatment with dimethyl sulphate and potassium carbonate in acetone. The corresponding acetate (1 1) was treated with boron trifluoridediethyl ether at 60 "C for 30 min to give the product (13) of Fries rearrangement, together with deacylated material (9) which could be recycled, thereby providing a high yield of (13). The assignment of structure (13) t Compound (2) is already known.6 However the yield (34%) in the final step made an alternative route desirable for further synthesis. O/H.. M e 0 0 A c R ' & M e R 03 OMe OMe (11) R = H (12) R = O M e (13) R = H (14) R OMe 5,7-Dimethoxy-1,4-naphthoquinone (8) could be converted similarly into its 3-acetyl derivative (3) via the sequence (8) --+ (10) -(12) -(14) -(3). Assignment of struc ture (10) to the product of reductive monomethylation of (8) rested on a comparison with the conversion of (7) into (9) and also the appearance of a sharp, lowfield, concentrationindependent singlet at 6 8.72 for the hydrogen-bonded hydrogen [the corr...

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Synthesis of the aphin-related (±)-7,9-dideoxyquinone A and (±)-7,9-dideoxyquinone A′

Cited by 20 publications

References 1 publication

A model for the synthesis of naturally occurring benzisochromenequinones

A model for the synthesis of naturally occurring benzisochromenequinones

The stereoselective formation of naphtho[1,2-c]pyrans, angular analogues of the aphin-derived glucoside B, by an intramolecular version of the Mukaiyama reaction of 4-naphthyldioxolanes

The acetylation of naphthoquinones. The synthesis of 3-acetyl-5-methoxy- and 3-acetyl-5,7-dimethoxy-1,4-naphthoquinones

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