Ethers, methoxymethyl

It was thought that the acetal might have reacted with peroxy reagents, forming explosive peroxides. It was suggested that this could also occur with compounds such as tetrahydrofuranyl acetals, 1,3-dioxolanes, and methoxymethyl ethers. 

This derivative is stable to TsOH/benzene at reflux and to Cr03/H. It is stable to NBS// . In the formation of this derivative formaldehyde from formalin can react with a C,-hydroxyl group to form a methoxymethyl ether. Paraformaldehyde can be used to avoid formation of the ethers. ... 

R SiBr, trace MeOH. Methoxymethyl ethers are stable to these cleavage conditions. Methoxymethyl esters are unstable to silica gel chromatography, but are stable to mild acid (0.01 N HCl, EtOAc, MeOH, 25°, 16 h)." ... 

The hindered 11 )5-hydroxyl group fails to react with dihydropyran. However, mixed acetals [e.g., methoxymethyl ether (97)] and hemiacetals e.g., hydroxymethyl ether (98)] are obtained as by-products in the formation of the BMD group. ... 

Aldol condensation of the methoxymethyl ether of m-methoxybenzaldehyde (83) with cyclohexanone affords the conjugated ketone 84. Michael addition of dimethyl amine leads to the ami noketone Reduction of the ketone... 

The carbenoid displacement reaction (see Section 1.4.5.2.1.4.) of the optically active acetoxy sulfide derivative 19 (or the corresponding methoxymethyl ether) with diazomalonate in the presence of a catalytic amount of rhodium acetate in refluxing benzene affords the tram-alkylation productl22. 

In the first total synthesis of thromboxane A2, lactone 340 is opened by potassium trimethylsilanolate 97 to give the potassium salt 341 [120]. The potassium salt of the methoxymethyl ether of salicylic acid is prepared likewise [121], as are... 

The methyl and methoxymethyl ether derivatives, however, can be hydro-genolyzed without loss of enantiomeric purity (Scheme 4.76).319... 

The synthesis of the second Stille coupling partner 34 was efficiently achieved in three steps. First, 2-bromojuglone (36) [28] was protected as its methoxymethyl ether (46, Scheme 3.7). The quinone was reduced using sodium thiosulfate, and the resulting hydroquinone was protected with methoxymethyl chloride to afford the arene 47. Finally, stannylation using tetrakis-(triphenylphosphine)palladium and hexabutylditin [29] afforded the cross-coupling partner 34 in high yield. 

The methoxymethyl ether protecting groups of 33 were then cleaved using triphenylphosphine and carbon tetrabromide. The resulting hydroquinone function was oxidized by palladium on carbon under an atmosphere of air to afford the quinone 52 (70 %). A two-step procedure was implemented to install the diazo function. First, the ketone function of 52 was condensed with N,N -bis( tert-butyldimethylsilyl)hydrazine in the presence of scandium triflate, which formed the Af-tert-butyldimethylsilyl hydrazone 53. The hydrazone (53) was then oxidized using difluoroiodobenzene to afford kinamycin C (3) in 35 % yield. 

Our retrosynthesis of (—)-kinamycin F (6) is shown in Scheme 3.20 [45]. It was envisioned that (—)-kinamycin F (6) could be prepared from the protected diazofluorene 114 by conversion of the ketone function of 114 to a trans-], 2-diol, followed by deprotection of the acetonide and methoxymethyl ether protecting groups. The diazofluorene 114 was envisioned to arise from diazo transfer to the hydroxyfulvene 115. The cyclopentadiene substructure of 115 was deconstructed by a two-step annulation sequence, to provide the bromoquinone 116 and the p-trimethylsilylmethyl unsaturated ketone 117. The latter two intermediates were prepared from juglone (118) and the silyl ether 119, respectively. 

The synthesis of the naphthoquinone 116 is shown in Scheme 3.24. Bromination of juglone (118) afforded the dibromojuglone derivative 134. Protection of the phenol group as its methoxymethyl ether formed the product 135 (50 % yield over two steps). Finally, the C-3 bromide substituent was regioselectively substituted with methoxide by heating 135 in methanol in the presence of sodium carbonate (96 %). The methoxy group was installed to impart electronic bias to the naphthoquinone in the TASF(Et) coupling (vide infra). 

Enamides, in addition to the acrylates shown above, are also asymmetrically hydrogenated with many of the same systems that prove useful for the acetamidoacrylate reductions. The Rh(I)/BICP (2(/J)-2/(i)-bis(dipenylphosphino)-1(R),] (R)-dicyclopenlane) 132 and Rh(I)/DuPHOS systems work well (>90% ee) for the asymmetric hydrogenation of /3-acctamidovinyl methoxymethyl ethers... 

Hydroxyl groups protected as acetonides or as silyl, tetrahydropyranyl, benzyl, or methoxymethyl ethers are stable to these conditions. Yields with KMn04 are higher than those obtained with KMn04 and dicyclohexyl- 18-crown-6, Bu4NMn04, or NaMn04H20. ... 

Other acetal-type protecting groups (tetrahydrofurfuryl ethers, methoxymethyl ethers, 1,3-dioxolanes) are also considered to be incompatible with oxidising agents. 

Scleritoderma cf. paccardi, Spirophorida, Pori 24(/f)-methyl-5a-cholest-7-enyl 3p-methoxymethyl ether (sterol methoxymethyl ether)/cytotoxic on human tumor cells Gunasekera 1996B... 

Gunasekera, S.P. Kelly-Borges, M. Longley, R.E. (1996B) A new cytotoxic stCTol methoxymethyl ether from a deq) water marine sponge Scleritonema sp. cf. paccardi. J. Nat. Prod., 59, 161-2. 

Acylation of (S)-2-pyrrolidinemethanol (1) with aroyl chlorides provides amides 2 which, when treated with base and iodomethane or chloro(methoxy)methane, furnish the corresponding methyl or methoxymethyl ethers 3. 

If chelation of the metal was more efficient, by switching from a fert-butyl ether to a methoxymethyl ether, the use of an excess of ZnBr2 was efficient at accelerating... 

Stereoselective reduction of a 2-chloro-1,3-diketone. The reduction of I (nonenolizable) proceeds predominately anti with respect to the C—Cl bond. The chlorine atom in the product can be removed by zinc dust reduction of the methoxymethyl ether. 

Methoxymethyl ethers, 354 (S>-< + )-2-Methoxymethylpyrrolidine, 326 (E,Z)-l-Methoxy-2-methyl-3-trimethylsilyloxy-1,3-pentadiene, 326-327 (Z)-2-Methoxy-l-(phenylthio)-l, 3-butadiene, 328... 

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