Ethoxyethyl EE

EE-protected lactaldehyde 606 is readily available from lactate 310 in two steps by reduction of the ester with lithium aluminum hydride to give (5)-2-ethoxyethyl-1,2-propanediol (311) followed by Swem oxidation to the aldehyde [189]. 

In the synthesis of L-acosamine, condensation of the predominant isomer 609 with the magnesium enolate of tert-hutyl acetate gives 610 in 54% yield. Acetylation to 611 (77% yield) and subsequent catalytic hydrogenation in an autoclave (70 Kg/cm ) furnishes 612 as a single isomer. Acid hydrolysis of the ketal, benzoylation under Schotten—Baumann conditions, and lactonization affords 613. Reduction of the lactone to a lactol with diisobutyl-aluminum hydride gives N- benzoyl-L-acosamine (614) as an anomeric mixture. 

An identical series of reactions using the minor isomer 608 furnishes A-benzoyl-L-daunosamine (615) in comparable yield. 

Chiral butenolides are versatile intermediates in asymmetric synthesis. In particular, (S)-(+ )-jS-angelica lactone (260) is extremely useful for the synthesis of y-valerolactone natural products. It can be prepared in a straightforward manner by Wittig olefination of 606 with (ethoxycarbonylmethylene)triphenylphosphorane, which gives pentenoate 616 as an 82 18 mixture of Z and E isomers. After separation of the isomers by column chromatography, the desired (Z)-616 is simultaneously deprotected and lactonized by treatment with a catalytic amount of sulfuric acid to furnish 260 in nearly quantitative yield [191]. 

Azadirachtin (618), a terpenoid with strong antifeedant activity, possesses a unique bicyclic acetal subunit. Retrosynthetic analysis indicates that the intermediate 619 would be a suitable candidate for use in a convergent synthesis of the natural product. 

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Replacement of the tosylate group in 35 with a saturated butyl chain is achieved with an excess of lithium di-n-butylcuprate and, after hydrolytic cleavage of the isopropylidene and ethoxyethyl (EE) protecting groups, lactone 23 is obtained in an overall yield of... 

There is one example in which an ethoxyethyl (EE) protecting group is removed from a phenol during a Mukaiyama oxidation. According to the authors, this deprotection is promoted by a selective complexation of one oxygen with a magnesium atom.80... 

The 1-ethoxyethyl (EE) protecting group can be introduced by reaction of the appropriate malate ester with ethyl vinyl ether in the presence of an acidic catalyst, such as pyridinium p-toluenesulfonate [14] or trifluoroacetic acid [15,16]. In either case, the (AS)-malate ester EE ether 9 is isolated in quantitative yield. 

The 2-(phenylsulfonyl)ethyl ester Is stable to acidic conditions [tetrahydropyranyl (THP), tert-butoxycarbonyl (BOC), and ethoxyethyl (EE) groups can be selectively removed], and to oxidation (peroxide) but can be readily removed by treatment with DBU. Note that In both examples cited above, the 2- (phenylsulfon-yl) ethyl ester was cleaved without causing epimerization of the acid. The closely related reagent, 2 (p-toluenesulfonyl)ethanol. 

TBDMS acyl enones were prepared by treatment of an ethoxyethyl (EE)-protected alkoxyallene with n-BuLi at —85 °C followed by treatment of resulting anion with TBDMSCl (eq 21). Acid hydrolysis of the OEE group led to the TBDMS acyl enones in good yield. ... 

Ethyl vinyl ether is also useful for hydroxy group protection. The resulting derivative (1-ethoxyethyl ether) is abbreviated as the EE group.156 As with the THP group, the EE group introduces an additional stereogenic center. 

Synonyms Acetic acid, 2-ethoxyethyl ester AI3-01955 BRN 1748677 CCRIS 3286 Cello-solve acetate CSAC EGEEA EINECS 203-839-2 Ekasolve EE acetate solvent Ethoxy-acetate 2-Ethoxyethanol acetate Ethoxyethyl acetate P-Ethoxyethyl acetate 2-Ethoxyethyl ethanoate Ethylene glycol ethyl ether acetate Ethylene glycol monoethyl ether acetate Glycol ether EE acetate Glycol monoethyl ether acetate NSC 8658 Oxitol acetate Oxytol acetate Polysolv EE acetate UN 1172. 

As an alternative to protection as ethers, alcohols can also be protected as acetals, the most common being tetrahydropyranyl ethers (THP-OR) and 1-ethoxyethyl ethers (EE-OR) (Table 7.7). Support-bound secondary aliphatic alcohols have been... 

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