Methanesulphonic esters, synthesis

The structure proposed for septicine (20), the dehydroindolizidine constituent of Ficus septica, has recently been confirmed by two independent syntheses. The first synthesis proceeded from veratraldehyde, which was condensed with homoveratric acid to give the unsaturated acid (21) this was then converted into the primary chloride (22) by standard methods. Alkylation of L-prolinol with this chloride gave the amino-alcohol (23), which was converted into its O-methanesulphonate ester. Reaction of this ester with sodium hydride in anhydrous... 

Augustamine, [109]. The stannylated inline 353 utilised in the synthesis of (-)-amabiline (346) also served as the advanced intermediate for the preparation (Scheme 65) of (-)-augustamine (493) [93,94]. Thus, treatment of the mixture of the lithium salts 355 and 356 with iodomethane furnished a 43 1 mixture of the two tertiaiy amines 494 and 495 respectively. The cij-diol, obtained on acid hydrolysis of the former was converted into the ortho ester 496, which on exposure to methanesulphonic acid underwent cyclisation via the carbenium ion 497 to (-)-augustamine (493) in 76% yield. 

The synthesis of glycidic esters in a two-phase solid-liquid system has been reported yields of between 32 and 92 % are obtained for eleven examples. 2,3-Dibromoalkyl esters react with excess sodium azide on heating to give 2-azido-2-alkenoic esters in 71 to 87 % yield over five examples. The chiral formamido-ester (71) reacts with oxomethylenebis-(3 f+-imidazolium) bis(methanesulphon-ate) (72), a non-basic dehydrating agent, to give the a-isocyano-ester (73) in 80 % yield with only 1 % racemization, as shown by the re-hydration of the product (73) (Scheme 38). ... 

Sulphonyl Peroxides.—Continuing interest in this class of compound is a consequence of their value in aromatic sulphonoxylation and in their addition to alkenes to give sulphonate esters. A useful electrochemical preparation of bis(methanesulphonyl) peroxide from sodium methanesulphonate makes available a reagent for the synthesis of methanesulphonates of less reactive aromatic hydrocarbons. 

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