Methanol In Presence Of Sodium Methoxide Research Articles

Electroorganic synthesis of benzathine

Benzathine is prepared in good yields from cyanobenzene by a combination of electrochemical hydrogenation and Kolbe electrolysis using nickel and platinum electrodes in the presence of methanolic sodium methoxide in an undivided cell.

Synthesis of Some 6-Substituted 5-Azacytidines

Protected 6-substituted benzyl, phenyl and chloromethyl derivatives of 5-azacytidine 8-10 have been prepared by addition of phenylacetyl- (2), benzoyl- (3) or (chloroacetyl)guanidine (4) to 2,3,5-tri-O-benzoyl-β-D-ribosyl isocyanate (1) and subsequent silylation-mediated cyclization of the obtained acyl(carbamoyl)guanidines 5-7. 4-Amino-6-phenyl-1,3,5-triazin-2(1H)-one (12) was obtained by condensation of carbamoylguanidine (13) with methyl benzoate in presence of methanolic sodium methoxide or by condensation of 13 with triethyl orthobenzoate in N,N-dimethylformamide. Stannic chloride catalyzed condensation of silylated 6-phenyl derivative 11 with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribose (14) in 1,2-dichloroethane afforded a 1.2 : 1 mixture of N1 and N3 nucleosides 9 and 15, respectively. Methanolysis of the protected compounds 8-10 and 15 gave the respective free nucleosides 16-19. The latter compounds inhibited the growth of bacteria E. coli B to a much lower extent than the unsubstituted 5-azacytidine.

Synthesis of some 1,3,6-trioxygenated isopentenylated xanthones: Constitution of garcinone A

The reaction of l,3-dihydroxy-6-methoxy- and 1,3,6-trihydroxy-xanthone with 1-bromo3-methylbut-2-ene in presence of methanolic sodium methoxide, to give corresponding 3-methylbut-2enylated xanthones, is described. Synthesis of 1,3,6-trihydroxy-2,4-bis(3-methylbut-2-enyl)-9H- xanthen-9-one, designed as garcinone A and reported as a natural product from the fruit-hulls of Garcinia mangostana (Guttiferae), has also been achieved. However synthetic xanthone is found to be different from natural garcinone A, therefore its constitution needs reinvestigation.

Synthesis of carpachromene and related isopentenylated derivatives of apigenin

Acacetin ( 4) on reaction with prenyl bromide in the presence of methanolic sodium methoxide yielded 6,8-di-C-prenyl-( 5) and 6-C-prenyl-( 10) derivatives. The former ( 5) formed the corresponding bisdihydropyrano derivative ( 8). Monomethyl derivative of 10 ( 12) gave monodihydropyrano derivative ( 13). DDQ reaction of 10 followed by methylation afforded di-O-methyl carpachromene ( 2); whereas that of 5 gave a mixture of 21 and 22. Nuclear prenylation of apigenin ( 3) in a similar way gave 6,8-di-C-C-prenyl-( 16), its 7-0-prenyl-( 15) and 6-C-prenyl-( 18) derivatives. DDQ reaction of 18 provided natural carpachromene. 1 The structure of the isopentylated apigenin isolated by Dreyer et al. 2 needs further consideration.

Cinnamylation studies of 5,7-dihydroxy-2-methylisoflavone and chromone

Cinnamylation of 5,7-dihydroxy-2-methyl-isoflavone and chromone with cinnamyl alcohol in the presence of aqueous acetic acid yields 6,8-dicinnamyl- and 8-cinnamyl- derivatives, respectively. On the other hand, cinnamylation with cinnamyl bromide in the presence of methanolic sodium methoxide affords the corresponding 6-cinnamyl derivatives along with the same dicinnamyl derivatives. Cyclodehydrogenation of the monocinnamyl derivatives with DDQ is sluggish and gives the corresponding flavenes only in small yields.

ChemInform Abstract: SYNTHESIS OF 8‐DEOXYGARTANIN, TRAPEZIFOLIXANTHONE AND RELATED XANTHONES

AbstractBei der Alkylierung des Trihydroxyxanthons (I) mit dem Butenylbromid (II) bilden sich neben natürlichem 8‐Desoxy‐gartanin (IIIa) die Derivate (IIIb) und (IIIc).

Synthesis of 8-deoxygartanin. Trapezifolixanthone and related xanthones

Reaction of 1,3,5-trihydroxyxanthone (6) with 3-methylbut-2-enyl bromide in the presence of methanolic sodium methoxide yields a mixture of 2,4-di(3-methylbut-2-enyl)-5-(3-methylbut-2-enyloxy) derivative (7), natural 8-deoxygartanin (3) and the 2-(3-methylbut-2-eny1)-5-(3-methylbut-2-enyloxy) derivative (8). Cyclodehydrogenation of (3) and (8) with DDQ affords natural trapezifolixanthone (5) and 5-(3-methylbut-2-eny1oxy)-6-deoxyjacareubin (9) respectively.

The synthesis of sericetin and related flavonols

Galangin when reacted with prenyl bromide in the presence of methanolic sodium methoxide yields 6-C-prenyl-(minor) and 6,8-di-CC-prenyl (major) derivatives. The latter on cyclodehydrogenation with DDQ yields natural sericetin along with isosericetin, and the former affords desprenyl sericetin.

Synthesis of derrubone and robustone

5,7-Dihydroxy-3′,4′-methylenedioxyisoflavone(III) has been synthesised by condensation of 2-hydroxy-4,6-dibenzyloxyphenyl-3,4-methylenedioxybenzyl ketone (I) with ethyl formate in the presence of sodium, followed by catalytic debenzylation. Treatment of this isoflavone with prenyl bromide in the presence of methanolic sodium methoxide yields a mixture of 6, 8 -di-C-prenyl(IV), 7-O-prenyl(V) and 6-C-prenyl(VI) derivatives, constitutions of which have been established by a study of their NMR and mass spectra. The last compound agrees with derrubone which on cyclodehydrogenation with DDQ affords robustone (IX), Since natural robustone has already been converted into robustone methyl ether which in turn has been transformed into the corresponding 3-phenyl-4-hydroxycoumarins robustin and its methyl ether, the present work constitutes the synthesis of all these natural products.