Methanesulfonyl chloride, selective

Selective sulfonylation of 1 A/i -tri-O-tritylsucrose (activated by Bu2SnO) with methanesulfonyl chloride in benzene afforded the 3-mesylated derivative, whereas the same process performed in toluene surprisingly provided the 4-mesylate in 50% yield. If triflic anhydride is used as the sulfonating reagent, the 4-triflate was obtained in 40% yield (Scheme 12).153... 

Compound 13p is treated with methanesulfonyl chloride in methylene chloride in presence of triethylamine to provide mesyl derivative 13q in which the three hydroxylic fiinctions at C-3, C-4 and C-5 have been protected selectively with three different groups. 

Hydroboration of the methyl enol ether in (275) and subsequent oxidation provided crystalline (276). The selective hydrolysis of the protected lactol followed by treatment with methanesulfonyl chloride generated the sensitive dihydropyran (277), which was treated directly with osmium tetraoxide to give (278) and (279). 

The partial hydrolysis of 4a with methanolic potassium hydroxide followed by selective carboxylic acid reduction with excess borane and treatment of the resulting monoalcohol with methanesulfonyl chloride affords methyl 4-0-methanesulfonyl-2,3-0-isopropylidene-L-threonate (43). Facile displacement of the mesylate with azide followed by ester hydrolysis and catalytic reduction to an amine provides 4-amino-4-deoxy-2,3-0-isopropylidene-L-threonic acid (44). Mild acidic deprotection and ion-exchange desalting of 44 yields (2i ,3 S)-4-amino-4-deoxy-L-threonic acid (45), which has been utilized for the preparation of anthopleurine 46, the alarm pheromone of the sea anemone Anthopleura elegantissima [4] (Scheme 11). 

Treatment of the acetonide of (107) with one mole of methanesulfonyl chloride at low temperature gave the monomesylate (108) contaminated with some dimesylate. In glycosides such as (8), the acidity of the 2-hydr03Qfl group is enhanced by the inductive effect of the acetal (100). This effect is absent in the present case, but the observed selectivity could conceivably reflect less hindrance of the 2-hydroxyl group. Scission of the derived oxirane with sodio diethyl malonate was non-regioselective, but the... 

The intramolecular 8n2 attacking strategy is shown in Fig. 3.18. With trans-diol 3.5b and pyruvic acid chloride in pyridine, hydroxypyruvate compound 3.42 was obtained in 68 % yield selectively. 8econdary hydroxyl group on ffie six-membered ring could be protected with methanesulfonyl chloride compound to... 

Synthesis of dienyl chloride 2.349, the dithiane coupling partner for dithiane aldehyde 2.338, was accomplished in five steps from commercially available cis-2-butene-l,4-diol (Scheme 2.72). To this end, monosilylation of 2.344 as the TBS ether and this allyl alcohol was then oxidized with accompanying Zto E isomerization by PCC [122] to afford the enal 2.346 in 73 % yield. a,]S-unsaturated ester 2.347 was accessed by the Still—Gennari modification [219] of the Homer-Wads worth-Emmons olefination in good yield and selectivity (92 %, Z/E — 16 1). Reduction of the resulting ester 2.347 to produce allyl alcohol 2.348, in turn was chlorinated by treatment with LiCl and methanesulfonyl chloride to furnish the requisite dienyl chloride 2.349. 

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