Applications of Cyclic Sulfates ofvic-Diols:  Synthesis of Episulfides, Olefins, and Thio Sugars

Abstract

A new efficient and expeditious one-pot synthesis of thiiranes and olefins from cyclic sulfates of vic-diols is described. Opening of cyclic sulfates with potassium thioacetate or potassium thiocyanate followed by treatment with sodium methoxide led to episulfides. Olefins were obtained when potassium selenocyanate was used as nucleophile, and the obtained monoesters were treated with sodium borohydride. This method was applied to acyclic polyols derived from chiral glycerine, 1,2-isopropylidenehexofuranoses with different subtituents at C-3, and dimethyl acetals derived from pentoses and hexoses. The methodology is highly versatile, and its applicability has been demonstrated by the synthesis of different 4- and 5-thiosugars by opening of the thiirane ring with sodium acetate or lithium aluminum hydride. Reduction with lithium aluminum hydride of the thiocyanate sulfate potassium salt obtained by the opening of cyclic sulfate with KSCN allowed the direct synthesis of 5-deoxy-4-thio- and 6-deoxy-5-thiosugars. Cyclic thiosugars with the sulfur atom in the ring are obtained by acidic hydrolysis of the 5-thiol derivatives of 1,2-O-isopropylidenehexofuranoses and 4-thiopentose dimethyl acetals. Using this method, an efficient synthesis of 5-thio-l-fucose as well as the synthesis of 2,5-dideoxy-4-thiofuranose is described.

Masked Thiol Sugars: Chemical Behavior and Synthetic Applications of S‐Glycopyranosyl‐N‐monoalkyl Dithiocarbamates

“…For these reasons they were chosen to further demonstrate the synthetic possibilities of S-glycosyl-N-monoalkyl DTCs. In particular, the novel compounds 3 B,Cc were treated with the cyclic sulfate derived from glucose 14 [33] (Scheme 5). The selection of this compound as a representative example of the cyclic sulfate family was based on the well-established value of cyclic sulfates derived from saccharides as building blocks for the preparation of a wide variety of sugar-related compounds on account of the combination of their straightforward and efficient formation and their high chemical stability and reactivity.…”

Estratégias para a síntese de desoxinucluosídeos

“…Os ribonucleosídeos são dióis cis e vicinais cuja conversão em olefinas pode ser realizada por diversos métodos 14 . Basicamente, esta transformação é viável através de duas metodologias diferentes: conversão direta e conversão a derivados que possam ser mais facilmente desoxigenados.…”

“…A conversão direta de dióis vicinais a alcenos pode ser efetuada, por exemplo, com organometálicos derivados do tungstênio 14,15 , titânio 16,17 ou com oxocomplexos de rênio 21 . Outros métodos utilizam reagentes que realizam derivatização in situ, como por exemplo, cloreto de trimetilsilila/iodeto de sódio 18 , trifenilfosfina/imidazol/iodo 19 e tribrometo de fósforo/ brometo cuproso/éter, seguida por reação com zinco em pó.…”

“…Sulfatos cíclicos e também sulfitos 150 são usados como substratos reativos para várias reações de substituição nucleofílica 14,38,154,155 . De forma similar aos epóxidos, sulfatos cíclicos podem ser abertos por ataque de uma variedade de nucleófilos aos seus átomos de carbono.…”

“…O sulfato gerado é um bom grupo de saída e pode ser subseqüentemente substituído por um nucleófilo, permitindo que ambas as hidroxilas do diol original sejam substituídas. Como o SO 4 = é um grupo de saída muito menos eficiente do que ROSO 3 -, a segunda substituição é melhor efetuada se ocorrer de modo intramolecular 14 . Tais propriedades tornam os sulfatos cíclicos sinteticamente muito versáteis, inclusive permitindo a síntese de olefinas de modo direto 37,[39][40][41] , ou indireto 14 .…”