Pillaromycin-A: structural and synthetic studies related to the sugar moiety, pillarose

Fraser‐Reid, Bert; Walker, David Louis

doi:10.1139/v80-429

Cited by 16 publications

(3 citation statements)

References 5 publications

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“…First of all, the particles are extremely porous, crumbling to a fine powder upon being touched lightly. Furthermore, these MgO samples have large surface areas (130-170 m1 2/g) and large pore diameters (25-75 Á).3 (17) Note that a high excess of D2 was employed to minimize complications due to approach to isotopic equilibrium. Although conversions were often carried to >50% good straight line plots of log (0" -) vs. time were always obtained.…”

Section: H2)5och2ch2cl][zrcl5(thf)] (I)4mentioning

confidence: 99%

Thermally activated magnesium oxide as a selective deuteration catalyst under mild conditions

Hoq¹,

Klabunde²

1986

J. Am. Chem. Soc.

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Section: H2)5och2ch2cl][zrcl5(thf)] (I)4mentioning

confidence: 99%

Thermally activated magnesium oxide as a selective deuteration catalyst under mild conditions

Hoq¹,

Klabunde²

1986

J. Am. Chem. Soc.

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“…The basic conditions are most probably responsible for this total isomerization to the single a-anomer. Alternatively, the deprotection was attempted using triethylamine in methanol-water, 10 but the yield was much lower at only 72%. The next step, involving the oxidation of the reactive allylic 4-hydroxyl function was achieved by either of two methods, namely using manganese dioxide (MnO 2 ) in dichloromethane (24 h at r.t., 65% yield), or the Dess-Martin periodinane method 11 With this versatile intermediate in hand, the following step was the key to our strategy, in which a [3+2] cycloaddition reaction would provide the novel pyranopyrrolidines in a single step.…”

mentioning

confidence: 99%

Regio- and Enantioselective Synthesis of Novel Functionalized Pyranopyrrolidines by 1,3-Dipolar Cycloaddition of Carbohydrates

Bashiardes¹,

Cano²,

Mauzé³

2005

Synlett

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A new methodology is described for the rapid enantiomeric synthesis of a novel series of pyranopyrrolidines from readily available and inexpensive carbohydrate compounds. The major feature of the method is a highly selective [3+2] cycloaddition reaction of different azomethine ylides with a chiral carbohydrate-derived enone. The reaction proved to be extremely regio-and stereoselective, giving rise to single enantiomeric compounds in all cases. Moreover, the method is totally atom-efficient and amenable to diversity, since structural diversity of the new compounds is dictated by the choice of the starting materials employed.Pyrrolidinic bicyclic systems are constituents of many biologically active compounds, such as, for example, antagonists of neuroexcitatory amino acids, 1 which intervene in disorders like epilepsies or Huntington's chorea. They are also useful as intermediates for total synthesis of more complex therapeutic molecules. 2 As such, it is of interest to develop the synthesis of such target molecules, using methods allowing control of stereochemistry and permitting diversity.One of the most versatile methods for the synthesis of pyrrolidines is the [3+2] cycloaddition reaction involving azomethine ylides derived from a-aminoesters, an aldehyde and a suitable dipolarophile. 3 The generation of azomethine ylides from imines by formal 1,2-prototropy, metal salt-tertiary amine combinations provides a simple, regio-and stereospecific process for the synthesis of polysubstitued pyrrolidines. 4 We describe herein a novel and potentially widely adaptable methodology for the synthesis of pyranopyrrolidines from carbohydrate derivatives using azomethine ylides (Scheme 1). The method is atom-economical, with no loss of chiral inducing fragments. Indeed, the carbohydrate moiety maintains its specific stereochemistry and induces regio-and stereoselectivity to the cycloaddition reaction, providing the new pyranopyrrolidines in a controlled manner.By this approach, we considered that an easily accessible common key intermediate would provide diversely substituted fused pyrrolidines when treated with a variety of 1,3-dipolar azomethine ylides. As such, our strategy uses commonly available carbohydrates and a short and flexible sequence of reactions, leading to the final key step.Thus, the synthesis of the chiral enone 5 5 was undertaken as indicated in Scheme 2, in which the required compound was prepared in few steps using commonplace reactions, the judicious choice of which led to a relatively high overall yield. This key intermediate then underwent cycloaddition reaction in a stereo-and regiocontrolled manner to afford the required compounds. In each case, a single isomer was obtained, indicating the excellent induction conferred during the cyclization.As an example starting material, we used the commercially available and inexpensive 1-bromo-tetra-O-acetyl glucose (1), which was firstly submitted to reductive elimination 6 using zinc/aqueous acetic acid to afford glycal 2 in 78% yield. Treatment with catalytic...

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“…Applications concerning the synthesis of natural C-branched sugars such as pillarose are given using this photoaddition methodology [61].…”

Section: 2220xicarbinyl Speciesmentioning

confidence: 99%

Synthetic saccharide photochemistry

Descotes

Carbohydrate Chemistry

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Synthetic photochemical applications to carbohydrates are described by photosubstitution, photoaddition, photoizomerisation, photoreduction, and photoxidation reactions. The use of photoremovable protecting groups in osidic syntheses is also evoked.The recent development of such radical reactions using photoinitiators is mainly due to their regio and stereoselectivities interpreted in terms of stabilized conformations of carbohydrate radicals by stereoelectronic factors. The preferential s-attack of anomeric radicals is a well documented example of such transformations.Some new methodologies using single electron transfer reactions are also indicated in this review.

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Pillaromycin-A: structural and synthetic studies related to the sugar moiety, pillarose

Cited by 16 publications

References 5 publications

Thermally activated magnesium oxide as a selective deuteration catalyst under mild conditions

Thermally activated magnesium oxide as a selective deuteration catalyst under mild conditions

Regio- and Enantioselective Synthesis of Novel Functionalized Pyranopyrrolidines by 1,3-Dipolar Cycloaddition of Carbohydrates

Synthetic saccharide photochemistry

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Pillaromycin-A: structural and synthetic studies related to the sugar moiety, pillarose

Cited by 16 publications

References 5 publications

Thermally activated magnesium oxide as a selective deuteration catalyst under mild conditions

Thermally activated magnesium oxide as a selective deuteration catalyst under mild conditions

Regio- and Enantioselective Synthesis of Novel Functionalized Pyrano­pyrrolidines by 1,3-Dipolar Cycloaddition of Carbohydrates

Synthetic saccharide photochemistry

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Product

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Regio- and Enantioselective Synthesis of Novel Functionalized Pyranopyrrolidines by 1,3-Dipolar Cycloaddition of Carbohydrates