Lithium epoxide ring opening with

The compound (70) by epoxide ring-opening with hydrogen fluoride, followed by photocatalysed addition of acetylene to the A16-bond and lithium aluminium hydride reduction, gave (71). Protection of the 1,2-diol system in (71) as the acetonide followed by oxidation, dehydration, and regeneration of the diol grouping produced... 

An improved synthesis of 3-cyano-3-deoxy- and 3-deoxy-3-formyl-hex-2-eno-pyranosides has been described. Thus treating methyl 2,3-anhydro-4,6-0-benzyl-idene-a-D-galactopyranoside with diethylaluminium cyanide (epoxide ring opening with CN) then elimination of water with diisopropylamine, lithium perchlorate and tosyl chloride afforded 39 which on reduction with DIBAL gave 40.34... 

Elaboration of 248 to 257 is depicted in Scheme 32. Acidic deketalization, basic epoxide formation, and silylation of the remaining hydroxyl group led to 249, which was subjected to ring opening with lithium dimethylcuprate in a regioselective (78 15) fashion to provide the desired alcohol 250 as the major... 

Chiral amino alcohols can be prepared by reaction of chiral epoxides with amines. Enantiopure (25, 3.R)-2,3-epoxy-3-phenylpropanol anchored to Merrifield resin has been used for ring-opening with secondary amines in the presence of lithium perchlorate to afford polymer-supported chiral amino alcohols 47 (Eq. 18) [56], By analogy, (2i ,35)-3-(cis-2,6-dimethylpiperidino)-3-phenyl-l,2-propanediol has been anchored to a 2-chlorotrityl chloride resin (48). Although this polymer had high catalytic activity in the enantioselective addition of diethylzinc to aldehydes, the selectivity of the corresponding monomeric catalyst was higher (97 % ee) in the same reaction. 

Exo- and endo-cyclic ring closure reactions using 0-nucleophiles transform oxocarbenium ions into cyclic acetals. As an example of an endocyclic cyclization, epoxide ring opening of (96) with lithium dimethyl cuprate, and subsequent treatment of the resulting alcohol with acid, smoothly gives the bicyclic acetal (97), ° a key intermediate in the total synthesis of tirandamycic acid (Scheme 47). ... 

Oxaspiropentanes are classified as a unique class of cyclopropyl ethers. Two reaction courses are recognized as being associated with the reaction in the presence of lithium bases. Treatment of oxaspiropentanes with butyllithium leads to S 2-type epoxy ring opening, giving butyl-connected cyclopropanols. On the other hand, with lithium amide as base there is deprotonation at the epoxy carbon followed by epoxide ring opening. The latter reaction offers a useful synthesis of 1-vinylcyclopropanols. ... 

Peric s and coworkers have elucidated a facile and inexpensive route to determining the enantiomeric excess of primary amines. A regioselective and enantioselective epoxide ring opening of 108 with BF, followed by lithium ferf-butoxide catalyzed epoxide closure yielded 109, which was utilized as a resolution reagent. Through the use of 20 mol% of 109 relative to an amine, an ee determination could be performed on 110 via NMR without further purification <05OL3829>. 

On nucleophilic attack, the epoxide ring opens according to the Furst-Plattner rule, with the formation of the di-axial derivative, because the pyranoid rings in the frons-linked derivatives (98) and (99) are completely fixed and the cfs-linked derivatives (100) and (101) are fixed to a considerable extent in the Cl form. (The corresponding members of the L series belong to the 1C form ) The 2-deoxy derivatives are prepared by the mercaptal method, and also, more easily, by direct reduction of the anhydro derivatives (98) and (100) with lithium aluminum hydride. Only the riho and xylo configurations, (102) and (104), are accessible (X = H), but these are obtained in very good yield. This... 

The trithiocarbonates may prove useful as intermediates for the synthesis of sugar dithiols from epoxides. Ring opening by reductive cleavage with lithium aluminum hydride gives excellent results with aliphatic and ahcyclic trithiocarbonates. When both carbon atoms are secondary, the product is a iraws-dithiol for example, cyclohexene oxide, which is converted into a irans-trithiocarbonate, gives, on reduction, cyclo-hexane-1,2-dithiol. The reaction has been used in the cyclitol series for the preparation of 1,2-dithio-neo-inositol and 1,2-dithio-ir-inositol, from 1,2-anhydro-alZo-inositol. The inositol trithiocarbonates show pronounced Cotton effects in their optical rotatory-dispersion spectra. 

The free hydroxy group in 880 is first protected as a benzoate, ring opened with the lithium anion of 1-heptyne, and finally tosylated to afford 881, which is deprotected and cyclized to the epoxide with potassium carbonate in methanol. A Lindlar reduction of the triple bond provides the cw-olefin present in ( —)-(6Z,97 ,10iS)-9,10-epoxyheneicosadec-6-ene (882). In order to prepare the enantiomer 884, 880 is directly ring opened with the lithium anion of 1-heptyne, and then tosylated to afford 883, which is cyclized and selectively reduced to (+ )-(6Z,95, 10/ )-9,10-epoxyheneicosadec-6-ene (884) [250] (Scheme 192). 

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