Methoxybenzyl protecting group

Treatment of 8-azidomethylperhydropyrido[l,2-c]pyrimidin-l-one 157 with methyl triflate and catalytic hydrogenation of the azide group led to the formation of tricyclic guanidine derivative 158 (01JA8851). Hydroxy group of 149 was protected with methoxymethyl chloride, and the p-methoxybenzyl protecting group (PMB) was eliminated by treatment with DDQ. 

The completion of the synthesis of the polyol glycoside subunit 7 requires construction of the fully substituted stereocenter at C-10 and a stereocontrolled dihydroxylation of the C3-C4 geminally-disub-stituted olefin (see Scheme 10). The action of methyllithium on Af-methoxy-Af-methylamide 50) furnishes a methyl ketone which is subsequently converted into intermediate 10 through oxidative removal of the /j-methoxybenzyl protecting group with DDQ. Intermediate 10 is produced in an overall yield of 83 % from 50) , and is a suitable substrate for an a-chelation-controlled carbonyl addition reaction.18 When intermediate 10 is exposed to three equivalents of... 

An intramolecular acetal has also been introduced by the treatment of a mixture of a 1-thio-mannoside, having a methoxybenzyl protecting group at C-2 and an alcohol with DDQ [71] (Scheme 4.4c). Activation of the thioglycoside with methyl triflate gave a P-mannoside as the only anomer. This approach was employed for the synthesis of the core pentasaccharide of N-linked glycoproteins. 

Reduction of benzylic oxygen functional groups with Raney nickel has occasionally been reported, but there are very few examples in the recent literature. Hydrogenolysis over W-2 Raney nickel has been used to selectively remove benzyl ether protection in the presence of a 4-methoxybenzyl protecting group (equation 30)." ... 

The jo-methoxybenzyl protecting group in tetrazole 401 was hydrogenolyzed without the cleavage of the hydroxy group (Scheme 119).ti i... 

This particular reaction allowed us to carry out the hitherto shortest synthesis of erythronolide A. The efficiency of this synthesis is clearly a consequence of both the stereoselective chain extension processes as well as the advantageous use of p-methoxybenzyl protective groups. 

Benzyl ethers have been removed in the presence of 4-bromobenzoates without debromination using anhydrous ferric chloride in dichloromethane and TFA in dichloromethane has been used to effect removal of 0-4-methoxybenzyl protecting groups. ... 

The precursor (121) for the A-ring was prepared in three steps from aldehyde (120). This compound was condensed with ketone (119) in a Borsche modification of the Friedlander reaction to give tetracyclic quinoline (122) (Scheme 18). Selective cleavage of the A-ring p-methoxybenzyl protecting group allowed further transformation to nitro compound (123). 

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