Utilisation d'ylides du phosphore en chimie des sucres. XX. Synthèse de sucres acétyléniques et réarrangment d'intermédiaires carbénoïdes. Communication préliminaire

Tronchet, J. M. J.; González, Anaisa Hernández; Zumwald, Jean‐Bernard; Perret, Françoise

doi:10.1002/hlca.19740570605

Cited by 32 publications

(9 citation statements)

References 6 publications

(1 reference statement)

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“…The enol-ether moiety of 4 and 6 gives rise to a s at 163.0 and 156.7, and to a d at 83.9 and 104.1 ppm. The same configuration of the C=C bond of 4 and 6 is revealed by similar chemical shifts for HÀC (5), HÀC(6), C(5), and C(6) of 4 and the corresponding 1 H-(Dd 0.06 ppm) and 13 C-NMR (Dd 0.6 ppm) signals of 6. The (Z)-configuration of 4 is suggested by similar d values for the enol ether 13 C s of 4 and of a closely related bicyclic (Z)-configured analogue [1] (163.0 vs. 164.2 ppm) differing clearly from that of the corresponding (E)-isomer (168.8 ppm) 1 ).…”

mentioning

confidence: 68%

Functionalised Monocyclic Five‐ to Seven‐Membered exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy Buta‐1,3‐diynes and 1‐Haloalkynols

Xu¹,

Miao²,

Bernet³

et al. 2005

Helvetica Chimica Acta

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Dedicated to András Lipták on the occasion of his 70th birthday Base-promoted (KOH or MeONa in MeOH, or NaH in THF) cycloisomerisation of partially benzylated, 1-substituted (R = PhÀCC, pyridin-2-yl, or Br) ald-1-ynitols leads to (Z)-configured five-, six-, and seven-membered exo-glycals. The reactivity of the ald-1-ynitols depends upon their configuration. The ald-1-ynitols were derived from 2,3,5-tri-O-benzyl-D-ribofuranose 1, and the corresponding, partially O-benzylated galactose, glucose, and mannose hemiacetals by ethynylation. The hex-1-ynitol 2 derived from 1 (61%) was transformed via the 1-phenylbuta-1,3-diyne 3 and the 1-(pyridin-2-yl)acetylene 5 into the five-membered exo-glycals 4 and 6 (in 66 and 72% yields, resp., from 2). The analoguous ethynylation of 2,3,4,6-tetra-O-benzyl-D-galactose 8 was accompanied by elimination of one benzyloxy (BnO) group to the hept-3-en-1-ynitol 9 (71%), which was transformed into the non-5-ene-1,3-diynitol 10 and further into the six-membered exo-glycal 11 (50% from 9). Addition of Me 3 SiCCH to the galactose 8 and to the gluco-and manno-analogues 16 and 24 gave epimeric mixtures of the silylated oct-1-ynitols (86% of 12L/12D 45 : 55, 94% of 17L/17D 7 : 3, and 86% of 25L/25D 55 : 45), which were separated by flash chromatography, and individually transformed into the corresponding 1-bromooct-1-ynitols. Upon treatment with NaH in THF, only the minor epimers 13L, 18D, and 26D cyclised readily to form the seven-membered hydroxy exo-glycals. They were acetylated to the more stable monoacetates 14L, 23D, and 28D (82 -89% overall yield). Under the same conditions, the epimers 13D, 18L, and 26L decomposed within 12 h mostly to polar products. The difference of reactivity was rationalised by analysing the consequences of an intramolecular C(3)OÀH ··· À OC (7) H-bond of the intermediate alkoxides on the orientation of À OÀC(7) of 13L, 18D, and 26D and its proximity to the ethynyl group.Introduction. -We have recently reported our investigations on the base-promoted alkynol cycloisomerisation of buta-1,3-diynlated and haloethynylated glycopyranosyl and -furanosyl alcohols to bicyclic exo-glycals [1]. In this paper, we describe the results of the alkynol cycloisomerisation of buta-1,3-diynlated, bromo-, and (pyridin-2-yl)ethynylated alditols to monocyclic exo-glycals of different ring size.In the course of the structure elucidation of naturally occurring oligoacetylenes, Jones et al. [2] and Bohlmann et al.[3] discovered the base-catalysed 5-exo-dig cyclisation of hydroxylated oligoacetylenes to 2-methylidene-oxolanes. This alkynol cycloisomerisation is favoured when the alkynyl group is activated, as in cumulated triple bonds, or by substitution with a 1-bromo, 1-chloro, 1-phenylchalcogeno (S or Se), or 1-(het)aryl group, and also by the proximity of the reacting groups, as in cyclic starting materials [1] [4 -6]. Activation of an isolated alkynyl group by coordination with a Lewis acid also promotes the cycloisomerisation [7]. In most cases, cyclosiomerisation resulted in (Z)-co...

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confidence: 68%

Functionalised Monocyclic Five‐ to Seven‐Membered exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy Buta‐1,3‐diynes and 1‐Haloalkynols

Xu¹,

Miao²,

Bernet³

et al. 2005

Helvetica Chimica Acta

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“…Ces travaux ont fait l'objet de publications preliminaires [5] [8]. [14] a t t t appliqute aux composts 1 et 2.…”

Section: Discussionunclassified

“…C60,59 H 7,12% Tr. C 60,71 H 7,16% (d,J2,3=5,8,I H,); 4,79 (dxd, 53,4'0,4, J4,6=2,6, 1 H, H-C(4)); 4,91 (dxd, 1 H, H-C(3)); [3,4: 5,6]-/~'-D-arabino-heptyne-l -ulo-3-pyrannose-3.7 (21). A partir de 1,5 g (3,6 mmol) de dibromoenose 14 trait6 comme decrit pour la preparation de 15, on obtient 533 mg (58%) de 21: Rf 0,45 (hexane/EtlO 1: I); sirop, Eb.…”

Section: Anhydro-36-o-isopropylid~ne-45-~-ribo-hexyne-i-t~trolunclassified

Préparation de dérivés de sucres acétyléniques terminaux et d'acides ynuroniques par réaction de Wittig. Note de laboratoire

Tronchet

Bonenfant

Perret

et al. 1980

Helvetica Chimica Acta

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The method described for the preparation of terminal acetylenic sugars presents two advantages over earlier procedures: no new asymmetric center is created and the chain can be extended by one or more C-atoms. The method also allows preparation of ynuronic acids. The aldehydosugars derivatives 1-7 gave in good to excellent yields the corresponding gem-dibromoenoses 8-14 from which either the terminal acetylenic sugars derivatives 15-21 or the ynuronic acids 22-24 were easily prepared. A few examples of 1,3-dipolar cycloadditions (leading to 28-30) with these acetylenic sugar derivatives are also described.

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“…A very early example of the use of carbenoids for carbohydrate functionalization in combination with chain elongation came from Tronchet et al Keto sugars (e.g., 119 ) were treated with dimethyl diazomethylphosphonate, which gave the intermediate carbenoids, and subsequent C–H insertion yielded products such as 120 (Scheme ).…”

Section: C–h Activation Of Carbohydrate Protecting Groupsmentioning

confidence: 99%

C–H Functionalization on Carbohydrates

2016

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Functionalization of C-H bonds has received significant attention in organic chemistry during the last decade and it is still a "hot" topic. In particular, C-H modification of natural products has benefitted from this development. Carbohydrates are densely functionalized natural products, and methods for their functionalization are therefore very attractable. This review presents methods from the last five decades and gives an over-

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Utilisation d'ylides du phosphore en chimie des sucres. XX. Synthèse de sucres acétyléniques et réarrangment d'intermédiaires carbénoïdes. Communication préliminaire

Cited by 32 publications

References 6 publications

Functionalised Monocyclic Five‐ to Seven‐Membered exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy Buta‐1,3‐diynes and 1‐Haloalkynols

Functionalised Monocyclic Five‐ to Seven‐Membered exo‐Glycals by Alkynol Cycloisomerisation of Hydroxy Buta‐1,3‐diynes and 1‐Haloalkynols

Préparation de dérivés de sucres acétyléniques terminaux et d'acides ynuroniques par réaction de Wittig. Note de laboratoire

C–H Functionalization on Carbohydrates

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