3,4-Dimethoxybenzyl carbonates

Anodic oxidation of 4-(3,4-dimethoxybenzyl)-6,7-dimethoxy-2-methyl-l,2, 3,4-tetrahydroisoquinoline (168) in trifluoroacetic acid-dichloromethane-Bu4NBF4, using controlled-potential electrolysis (-I-1.2V versus SCE) affords the corresponding 3,4-dihydroisoquinolinium salt (169), and the 4-(3,4-dimethoxybenzylidene)-6,7-dimethoxy-2-methyl-3,4-dihydroisoquino-linium salt (170) was formed at higher anodic potential (+1.9V versus SCE) at a carbon-felt anode256 [Eq. (104)]. 

The assignments of the 13C chemical shifts of laudanosine were first made by Wenkert et al. (6) and confirmed later (15). It is now apparent that compounds 2 and 3 (14) and 3,4-dimethoxyphenethylamine (6, 15) serve as satisfactory models of the isoquinoline and benzyl moieties, respectively. The substitution of a 3,4-dimethoxybenzyl group at C-l of 3, as in laudanosine (28), caused changes to occur in the chemical shifts of the aliphatic carbon atoms of the tetrahydroisoquinoline moiety analogous to those of the compounds with substituents at C-l listed in Table II (C-l, +7.9 C-3, —6.2 C-4, —3.5 NCH3, —3.6). The chemical shift changes between 27 and 28... 

A one-pot approach giving a series of l-(2-naphthyl)methylene- or l-(3,4-dimethoxybenzyl)pyrrolidines 432 has been developed, as illustrated by the reductive cyclization of the four-carbon precursor 433, which was prepared by conjugate addition of the a-(alkylideneamino)nitrile 434 to methyl vinyl ketone (Scheme 55) <2005S945>. 

Analogous behavior is also observed with the corresponding 3,4-dimethoxy derivatives [102] with these derivatives, however, because of the increased stability of the radical cations, in acidic solution a decrease in reactivity of three orders of magnitude for the deprotonation reaction is observed on going from MBA to the 3,4-dimethoxybenzyl alcohol radical cation (veratryl alcohol, VA). In the presence of OH the deprotonation site shifts from carbon to oxygen, as previously described for the 4-methoxy derivatives, and a dramatic increase in reactivity is observed, VA + reacting with OH with A = 1.3 x 10 M s (Table 5), a value which is lower than the diffusion limit and which, compared with that measured for MBA +, rather than the decreased O-H acidity of VA , presumably reflects the increased electron density on the aromatic system which disfavors the intramolecular (side-chain to nucleus) electron transfer eventually leading to the benzyloxyl radical. 

Peptide synthesis, N-protection Acetic-formic anhydride. Adamantyl chloroformate. Benzylthiocarbonyl chloride. /-Butoxycarbonyl-N-hydroxysuccinimide ester. /-Butyl azido-formate. /-Butylcarbonic diethylphosphoric anhydride. /-Butyl fluoroformate. /-Butyl oxycarbonyl fluoride. /-Butyl pentachlorophenyl carbonate. /-Butyl 2,4,5-trichlorophenyl carbonate. Carbobenzoxy chloride. 3,5-Dimethoxybenzyl p-nitrophenyl carbonate. [2-(Diphenyl)isopropyljphenyl carbonate. /-Pentyl chloroformate. 

An aryl-alcohol oxidase produced optimally under carbon limitation from Bjerkandera adusta oxidized a number of benzyl alcohols including 4-methoxybenzyl alcohol, 3,4-dimethoxybenzyl alcohol (veratryl alcohol), and 4-hydroxy-3-methoxybenzyl alcohol, with the production of H202 from 02 monosaccharides were not oxidized (Muheim et al. 1990). An aryl-alcohol oxidase from Pleurotus eryngii is a flavoprotein with range of substrates comparable to that from B. adusta (Guillen et al. 1992). 

A soln. of 3,4-dimethoxybenzyl p-methoxyphenyl carbonate in hexamethylphos-phoramide heated to 140° when steady COg-evolution occurs, and kept at this temp, until conversion is complete after 1 hr. 3,4-dimethoxybenzyl p-methoxy-phenyl ether. Y 93%. F. e. s. J. M. Prokipcak and T. H. Breckles, Can. J. Chem. 49, 914 (1971). 

Obtained by reaction of methylene iodide with 2,4,5-tri-hydroxy-6-methoxyphenyl 3,4-dimethoxybenzyl ketone in the presence of potassinm carbonate in refluxing acetone for 45 h [5559]. 

Preparation by partial methylation of 2,4,6-tri-hydroxy-3-methylphenyl 2, 3-dimethoxybenzyl ketone with dimethyl sulfate in the presence of potassium carbonate in boiling acetone (69%) [5483],... 

In the starting material, the dimethoxybenzyl group is in the up position on the chiral carbon, from the perspective drawn. This group thus attacks the P carbon of the a,P-unsaturated ketone from the top face, pushing the other aromatic ring down , so that it ends up cis to the hydrogen on the adjacent chirality center. 

---