Lithium mesylate reduction with

Ozonolysis of alkene 446 in the presence of acetaldehyde afforded diketone 448 through the intermediacy of 447. Ring expansion through Beckmann rearrangement took place when bis-oxime 449 was mesylated and warmed in aqueous tetrahydrofuran (THF). The bis-lactam so formed gave piperidinediol 450 on reduction with lithium aluminium hydride, and this compound was transformed into ( )-sparteine by treatment with triphenylphosphine, CCI4, and triethylamine (Scheme 105) <20050BC1557>. 

The CD fragment 1s synthesized starting with resolved bicyclic acid 129. Sequential catalytic hydrogenation and reduction with sodium borohydride leads to the reduced hydroxy acid 1. The carboxylic acid function is then converted to the methyl ketone by treatment with methyl-lithium and the alcohol is converted to the mesylate. Elimination of the latter group with base leads to the conjugated olefin 133. Catalytic reduction followed by equilibration of the ketone in base leads to the saturated methyl ketone 134. Treatment of that intermediate with peracid leads to scission of the ketone by Bayer Villiger reaction to afford acetate 135. The t-butyl protecting... 

An efficient synthesis of ( )-quebrachamine is based on the construction of a suitable precursor via ring cleavage of an a-diketone monothioketal (810) (80JCS(P1)457). This monothioketal, available from 4-ethoxycarbonylcyclohexanone ethylene ketal, was fragmented to the dithianyl half ester (811) with sodium hydride in the presence of water. Reaction of (811) with tryptamine and DCC provided an amide which was converted to the stereoisomeric lactams (812) on hydrolysis of the dithiane function. Reduction of either the a- or /3-ethyl isomer with lithium aluminum hydride followed by conversion of the derived amino alcohol to its mesylate produced the amorphous quaternary salt (813). On reduction with sodium in liquid ammonia, the isomeric salts provided ( )-quebrachamine (814 Scheme 190). 

The aldehyde (163), which was prepared from 160 by periodic acid oxidation, was further converted into pseudo-a-D-mannopyranose as follows. Dehydration of 163 with mesyl chloride and pyridine, and subsequent reduction with lithium aluminium hydride gave (3S, 4R, 5S)-3,4,5-tris(benzyloxy)-l-cyclohexene-1-methanol (164). Hydroxyla-tion of 164 with diborane and hydrogen peroxide yielded 4,6-di-0-acetyl-l,2,3-tri-0-... 

The trachylobane ring system has been synthesized by homoallylic reduction of the atisene mesylate (83) with lithium aluminium hydride.79 The structure of many of the... 

Dihydroxylation of the stilbene double bond in the trans isomers of Combretastatin A-1 and A-4 produced diols which by treatment with boron trifluoride in ethyl ether [44] or with trifluoroacetic acid [17] resulted in pinacolic rearrangement to produce an aldehyde. The aldehyde was converted in a variety of derivatives, as illustrated in the Scheme 20, via the following reaction sequence reduction with sodium borohydride to primary alcohol which was derivatized to the corresponding mesylate or tosylate, substitution with sodium azide and final reduction to amine with lithium aluminum hydride. Alternatively the aldehyde was converted to oxime which was catalitically hydrogenated to amine [17]. 

Starting with (54), the hydroxy-group was removed by mesylation and subsequent reduction with lithium aluminium hydride. The resulting compound (55) was converted into the pentacyclic methyl ether (56) using the analogous reaction sequence employed for the previously described synthesis of (52). Birch reduction of (56) and reacetylation yielded the enol ether (57). This compound was hydrolysed with dilute oxalic acid to the unsaturated ketone (58). Reduction with sodium borohydride followed by mesylation and treatment... 

Reduction of a mesylate. The last step in a total synthesis of the lignan ( )-schizandrin (2) involved reduction of the secondary hydroxyl group of 1. This was accomplished by reduction of the monomesylate of 1 with NaBH in DMF at 80°. Reduction of the mesylate with lithium triethylborohydride or with... 

Suyama and Gerwick reported a shorter, more practical route to both enantiomers of epiquinamide from the commercially available L-omithine derivative 2127 or its enantiomer.The route to (+)-epiquinamide (2104) is illustrated (Scheme 268). After conversion of 2127 into the Wein-reb amide (—)-2128, reaction with aUylmagnesium bromide produced the ketone (+)-2129, which required no purification apart from washing and extraction. Highly diastereoselective chelation-controUed reduction with lithium tri(teft-butoxy) aluminum hydride followed by mesylation gave the crystalline mesylate (—)-2130, which also did not require chromatographic... 

The mesylate group, introduced with methanesulfonyl chloride, can be cleaved with lithium aluminum hydride and dissolving metal reduction (Na, /-BuOH, HMPT, NH3, 64% yield). ... 

The azidohydrins obtained by azide ion opening of epoxides, except for those possessing a tertiary hydroxy group, can be readily converted to azido mesylates on treatment with pyridine/methanesulfonyl chloride. Reduction and subsequent aziridine formation results upon reaction with hydrazine/ Raney nickel, lithium aluminum hydride, or sodium borohydride/cobalt(II)... 

The azido mesylate may also be reduced with lithium aluminum hydride in the same manner as previously described for iodo azide reductions. The sodium borohydride/cobalt(II)tris(a,a -dipyridyl)bromide reagent may be used, but it does not seem to offer any advantages over the more facile lithium aluminum hydride or hydrazine/Raney nickel procedures. 

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