Methyl ethers trimethyl ether

Earlier attempts by Elarreri and by Macbeth and Mackay to prepare tri-O-inethylglyeogen (OMe, 45.6%) by direct methylation of the polysaccharide had not been successful, but gave partially methylated products of OMe 32-37 %. Haworth and coworkers found, however, that by simultaneous deacetylation and methylation of glycogen triacetate, followed by five or six further methylations, a trimethyl ether (OMe, 43.7) could be isolated in 90 % yield. The preliminary acetylation, during which degrada-... 

The structure of compound A was established in part by converting it to known compounds Treat ment of A with excess methyl iodide in the presence of silver oxide followed by hydrolysis with dilute hydrochlonc acid gave a tnmethyl ether of D galactose Companng this trimethyl ether with known trimethyl ethers of D galactose allowed the structure of compound A to be deduced... 

Tlie synthesis concludes by the route pioneered by Eschenmoser. Itromination of 47 proceeds at the position a to the tropolone I ing to give 48. Displacement of halogen by ammonia followed by liase hydrolysis of the tropolone methyl ether gives trimethyl-lolchicinic acid. Acetylation of the amine followed by reesteri-... 

Cyclohexanone, 23,35 Cyclohexene oxide, 137 Cyclohcxyl methyl ether, 137 l-Cydohexyl-2-methylpropene, 68-9 ( )-l-Cyclohexyl-2-trimethyl ilylethene, 12 (Z)-l-Cyclohexyl-2-trimethylsilylelhene, 12 l-Cydohcxyl-2-trimethylsilylethyne, 12 (2-Cyclohexylidene-eihyl)trimethylsilane, 29 Cyclopentadec-2-ynone, 48 Cydopentadiene, 25 Cyclopentanone, 72 Cyclopentenones, 15 Cyclopropanone, 133... 

This protocol could be extended to a range of different ,/i-unsaturated carbonyl compounds and either activated or deactivated aryl iodides [22], An application of related Heck chemistry to the synthesis of methylated resveratrol (3,4, 5-trihydroxy-( )-stilbene) is shown in Scheme 6.4 [23]. The phytoalexin resveratrol exhibits a variety of interesting biological and therapeutic properties, among them activity against several human cancer cell lines. Botella and Najera have shown that the trimethyl ether of resveratrol (Scheme 6.4) can be rapidly prepared by microwave-assisted Heck reaction of the appropriate aryl iodide and styrene derivatives, using the same oxime-derived palladacycle as indicated in Scheme 6.3. 

The naturally-occurring 1,6-linked glucose polymers furnish other sources of 2,3,4-trimethyl-D-glucose, which has been isolated from the hydrolysis products of the methyl ethers of gentiobiose,112 118 melibiose,114 raffmose106 116 and dextran.78 74,116... 

This particular trimethylglucose is unique in that it was separated in crystalline form from the hydrolyzates of the methyl ethers of several naturally-occurring glucose polymers almost two decades before it was synthesized from glucose. These natural sources, which still furnish the most convenient routes for the preparation of 2,3,6-trimethyl-D-glucose, include maltose,124-128 cellobiose,127,128 lactose,122-181 starch,71,182 glycogen,188,184 cellulose,185-187 and lichenin. 188,189 The literature pub-... 

It is now known1 that trialkyl phosphates will indeed alkylate phenols. The idea has been extended2 to the production of methyl ethers from alcohols and trimethyl phosphate, and of a butyl ether according to the equation... 

The same procedure has revealed that the aldobionic acid obtained from damson gum and cherry gum by acid hydrolysis has the structure V. Methylation gives the methyl ether VI and when this is subjected to hydrolysis with dilute mineral acid there results 3,4,6-trimethyl-D-mannose (VII) and 2,3,4-trimethyl-D-glucuronic acid (VIII). 

Bi s (tri methyl si lyloxy )cyclobut-l-ene Silane, (1 -cyclobuten-1,2-ylenedioxy)bis[trimethyl- Silane, [1-cyclobutene-1,2-diylbis(oxy)]bis[trimethy1- (17082-61-0), 65, 17 Boron trifluoride etherate Ethyl ether, compd. with boron fluoride (BFj) (1 1) Ethane, 1,1 -oxybis-, compd. with trifluoroborane (1 1) (109-63-7), 65, 17... 

The 1,11 -etheno-derivative (8) of oestrone methyl ether has an unusually flat structure, as a consequence of the presence of the extra aromatic ring." X-Ray analysis has established the geometry of 3a, 17a-dihydroxy-4,4,14a-trimethyl-19-nor-10a-pregn-5-ene-l 1,20-dione (9)" and the configuration of the S=0 bond in 2a,3a-epithio-5a-androstan-17/3-ol (R) S-oxide (10)."... 

The choice of an appropriate derivatisation of BAs is a crucial point for a good GC analysis [15]. Unconjugated BAs are commonly analysed as methyl ester-trimethyl-silyl (TMS) ether derivatives, although interference from plasma sterols may occur at the LCA retention time. Use of -butyl ester-TMS ether derivatives allows a better chromatographic separation between BAs, which elute later, and sterols. The advantage of this derivative procedure is the simplification of plasma pre-treatment. 

Cleavage of methyl and benzyl ethers.2 These ethers are cleaved by the combination of this silane and zinc iodide. The rate of dealkylation is enhanced by the presence of ( -C4H9)4NI. Trimethyl(methylthio)silane serves the same purpose. CH2C12 and C1CH2CH2C1 are satisfactory solvents. The cleavage probably does not involve in situ formation of iodotrimethylsilane. 

I S-Cycloalkanediones.1 In the presence of a zinc reagent prepared from Zn-Cu and this alkyl iodide, chloromethyl methyl ether reacts with 1,2-bis(trimethyl-silyloxy)cycloalkenes (I) to form 2-hydroxy-2-methoxymcthylcycloalkanones (2) (cf 8, 415). Ring-enlarged 1,3-cycloalkanediones (3) are formed from (2) by treatment with acid. 

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