5,6-dibromoprotocatechualdehyde and 2,3-dibromo-4,5-dihydroxybenzyl methyl ether

Total Synthesis of the Biologically Active, Naturally Occurring 3,4‐Dibromo‐5‐[2‐bromo‐3,4‐dihydroxy‐6‐(methoxymethyl)benzyl]benzene‐1,2‐diol and Regioselective O‐Demethylation of Aryl Methyl Ethers

“…The synthesis of 15 was performed according to the procedure described in [22]. Reaction of alcohols 6, 14, and 15 with Me 2 SO 4 in the presence of NaH gave benzyl methyl ethers 16 [23], 17, and 18 [22], respectively, in high yields (96, 96, and 94%, resp.). O-Demethylation of 16, 17, and 18 with BBr 3 in CH 2 Cl 2 at 0 -258 under N 2 , followed by addition of MeOH for deactivation of excess BBr 3 at 0 -608, afforded MeOCH 2 -substituted benzene-diols 19 [24], 20, and 21 [25], respectively, in high yields in a one-pot reaction (Scheme 2).…”

Sulfated bromophenols from Osmundaria obtusiloba (C. Agardh) R. E. Norris (Rhodophyta, Ceramiales)

“…Methylation of 2a gave the compound 2b which 1 H NMR spectrum (CDCl 3 ) presented a series of singlets at δ 7.0 (aromatic), 4.5, 3.9 and 3.8 that matched with the signals observed in the 1 H NMR spectrum for methylated lanosol (table1) (Katsui et al 1967). These facts suggested that the compound 2 is constituted by two 2,3-dibromo-4,5-dihydroxybenzylic groups, arranged in an asymmetrical way.…”

“…Its 1 H-NMR spectrum showed a pentasubstituted aromatic ring at δ 7.0 (1H, s) and a benzylic methoxymethylene group at δ 4.9, (2H, s) (table 1) (Katsui et al 1967). The carbon signals observed were: δ 135.3; 115.9; 122.9; 138.7; 149.7 and 118.1 and one at δ 71.1 (table 2).…”

Volatile halogenated metabolites from marine red algae

“…Bibliography: 1 Whitfield et al, (1999); 2 Kladi et al, (2003); 3 Weinstein et al, (1975); 4 Lim et al, 2000;5 Glombitza and Stoffelen, (1972); 6 Craigie and Gruenig, (1967); 7 Katsui et al, (1967); 8 Stoffelen et al, (1972); 9 Pedersen et al, (1974); 10 Chantraine et al, (1973); 11 Chevolot-Magueur et al, (1976); 12 De Nanteuil and Mastagli, (1981); 13 Kubo et al, (1990); 14 Blackman and Matthews, (1982).…”