Ethoxyethyl groups

Ethoxyethyl groups were chosen for the alcohol protection. Other protecting groups were tried but rejected for various reasons. TMS groups were easy to install and survived the subsequent DIBAL-H reduction but were lost in the Wittig reaction. The more stable TBDMS groups were used for initial stereochemical correlation experiments but were difficult to install and to remove. Various carbonates were made but had limited stability in the DIBAL-H reduction. 

The l-[2-(trimethylsilyl)ethoxy]ethyl group is a hybrid that combines the ease of protection using the l-ethoxyethyl group and the ease of deprotection of the SEM group. The protection is accomplished by reaction of a hydroxyl group... 

Protective group. In the presence of an acid the reagent reacts with the 2 -hydroxyl group of a ribonucleoside 3 -phosphate-5 -acetate to give the a-ethoxy-ethyl derivative. The a-ethoxyethyl group is preferred to the tetrahydropyranyl... 

Myoview is a TcOj complex, obtained by functional derivatization of l,2-bis(dimethylpho-sphino)ethane (DMPE) (Kelly et al. 1993). The chemical structure of Tc-tetrofosmin shows four phosphorus atoms of the bidentate diphosphine ligands, arranged in a plane (Fig. 2.1.11). However, tetrofosmin contains four ethoxyethyl groups, which ensure a rapid clearance of activity from the liver. The cationic charge facilitates myocardial uptake. 

Compound 12 was first subjected to the Hosomi-Sakurai reaction [6] to give 17, which was converted to 18 via m-chloroperbenzoic acid (MCPBA) oxidation etc. [7a, b]. The lithium salt of 19, derived from 1-0-benzylbutane-1,2(1 ), 4-triol, was added to 18 in tetrahydrofuran to give the adduct. Oxidation, desulfonylation, and removal of the benzylidene and ethoxyethyl groups gave the triol (20), which was readily converted to the aldehyde (segment B 16) [7b]. 

Stork and Raucher [76] have reported a chiral synthesis of PGA2 starting from 2,3-isopropylidene-L-erythrose from which they prepared the intermediate (85). Cyclisation with potassium t-butoxide in tetrahydrofuran and alkaline hydrolysis then afforded the keto acid (86a) which was transformed into PGA2 via reaction with lithium diisopropylamide and then phenyl selenyl chloride, oxidation of the product (86b) with sodium periodate and removal of the ethoxyethyl group. 

At some point during the synthesis of a target molecule, it may be necessary to protect an —OH group (i.e., to prevent its reacting). In addition to the trimethylsilyl, tert-butyl-dimethylsilyl, and other trialkylsilyl groups described in Section 11.6, and the tetrahy-dropyranyl group described in Section 16.7D, the ethoxyethyl group may also be used as... 

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