P-Methoxybenzyl Formate

Synonyms p-Anisyl formate Formic acid 4-methoxybenzyl ester 4-Methoxybenzenemethanol methanoate 4-Methoxybenzyl formate p-Methoxybenzyl formate... 

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 parallelism in reactions with HMPT and mixtures of phosphorus pentoxide and amines can best be realized by looking at the mechanism of HMPT reactions [1 5 ]. In the reaction of p-methoxy-benzylalcohol with HMPT which produce the corresponding N,N-dimethylbenzyl amine--p-methoxybenzyl phosphate was identified in the XP NMR spectrum of the reaction mixture. Since pyrophosphate was also observed during the reaction of the benzyl alcohol with HMPT, the intermediate formation of the metaphosphate anion can be assumed. Addition of the benzyl alcohol to that anion then produce the benzyl phosphate. Phosphate ions are known to be good leaving groups so that a benzylamine can easily be produced from the phosphate by reaction with di-methylamine released from the dimethylammonium ion. The phosphoric acid produced during the reaction is believed to react with HMPT, so that more dihydro-gen-bis(dimethylammonium) pyrophosphate is formed. 

Access to derivatives with protecting groups other than benzyl was also desired. Tri-O-acetyl-D-glucal (13) was deacetylated and benzylated with p-methoxybenzyl chloride to give 14. Cleavage of the olefin in 14 gave formate aldehyde 15. Hydrolysis of the formate ester led to lactol 16 and Wittig olefination then furnished the PMB protected olefin alcohol Id (Scheme 3). 

S-p-Methoxybenzyl Thioether RSCH2C6H4-/ -OCH3 (Chart 7) Formation... 

A mixture of 1-methyl-2-p-methoxybenzyl-3,4-diethyl-3-piperi-deine (156), 1 - methyl- 3,4-diethyl - 4 -p- metho xybenzyl- 2-piperideine (157), and 1-methyl- 2-(2-methyI-5-methoxyphenyl)-3,4-diethyl-3-piperideine (158) was obtained from 1-methyl- 1-p-methoxybenzyl-3,4-diethyl-3-piperideinium chloride (155). Compounds 156 and 157 were formed by the Stevens rearrangement, whereas the formation of compound 158 was due to the Sommelet rearrangement.1296... 

More sterically demanding ketones can influence the selectivity of dioxolane formation. For example, butane-1,2,4-triol reacts with 3-pentanone43 44 or 3,3-dimethoxypentane45 46 to give a mixture of the dioxolane 2SA and dioxane 28 5 in a ratio of 45 1 respectively [Scheme 3.28]. Enhanced preference for the dioxolane isomer is also observed in the reaction of 2-0-p-methoxybenzyl-t-threitol (29 1) with 3-pentanone [Scheme 3.29].47 48... 

An excerpt of a synthesis of the potent antitumour agent FR-900482 [Scheme 3.126] illustrates the use of an N, O-acetal with additional Af-protection in the form of a 2,2,2-trichloroethoxycarbonyl (TVoc) group (see section 8.3.7) in a multifunctional environment.244 245 The A 0-acetal survived the mildly acidic conditions required to deprotect the p-methoxybenzyl group that preceded the formation of the triflate 1263. Later, reductive cleavage of the Troc group and simultaneous hydrolysis of the oxazolidine ring was accomplished in a single... 

SYNS ANISYL FORMATE 2-(p-ANISYL)ACETIC ACID HOMOANISIC ACID 4-METHOXY-BENZENEACETIC ACID p-METHOXYBENZYL FORM.3TE 4-METHOXYPHENYLACETIC ACID MOPA... 

Cyclization of aspartic acid and asparagine to form aspartimides, and to a lesser extent of glutamic acid and glutamine to form glutarimide is an acid- and base-catalyzed common side reaction in peptide synthesis (see also Section 2.2.2). In SPPS it is particularly troublesome when Asp-Gly, Asp-Ala, and Asp-Ser sequences are present,but also with Asp-Asn.P P Piperidine-catalyzed aspartimide formation can be very rapid,and in this context DBU is even worse than piperidine.P The formation of aspartimide is reduced by the addition of HOBt or 2,4-dinitrophenol, but more efficiently it is reduced by protecting the aspartyl amide bond with the 2-hydroxy-4-methoxybenzyl (Hmb) group (see Section 2.3.2).P 1... 

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