Synthesis of Polyether Cyclophanes through Rhodium‐Catalyzed Cross‐Alkyne Cyclotrimerization

Abstract

Cross‐cyclotrimerizations of ether‐linked α,ω‐diynes and dimethyl acetylenedicarboxylate in the presence of a catalytic amount of cationic rhodium(I)/H8‐BINAP complex give [7]–[21]polyether cyclophanes in good yield. [8]–[9]Ester cyclophanes were also synthesized from the corresponding α,ω‐diynes. The ratio of para‐, meta‐, and orthocyclophanes depends on the length and the structure of the α,ω‐diyne tether chain, whilst the effect of concentration on the yield of polyether cyclophanes appears to be small. X‐ray analysis revealed that a single crystal of [15]metacyclophane 4g was the chiral form and that of [5.5]metacyclophane 4k the racemic form, due to an absence of ring flip in the crystals. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Chemistry and Biology of Oligovalent β‐(1→2)‐Linked Oligomannosides: New Insights into Carbohydrate‐Based Adjuvants in Immunotherapy

“…The NMR and mass spectral data were identical to those that we reported previously. [31] 1,3-Di[1-(2,3,4,6-tetra-O-acetyl-b-d-mannopyranosyloxyethyl)-4-(methyl-1-oxy)-1,2,3-triazolyl]propane (24): By following general procedure C, the azide-alkyne cycloaddition reaction between azidoethyl glycoside 8 (103 mg, 0.24 mmol) and compound 2 [20] (17 mg, 0.11 mmol) in the presence of copper(II) sulfate (5.4 mg, 0.03 mmol) and sodium ascorbate (13.3 mg, 0.07 mmol) gave the title compound 24 (102 mg, 93 %). R f = 0.30 (CH 2 Cl 2 /MeOH, 24:1); [a] 25 D = À22.18 (c = 1, CHCl 3 ).…”

“…Synthesis of oligovalent mannoside assemblies: To synthesize the target molecules, five different propargyl-based scaffolds 1-5 ( Figure 1) were selected for coupling with three different b-linked 2-azidoethyl mannosides (8,12, and 17) through azide-alkyne cycloaddition. Of these core molecules, propargyl alcohol (1) is commercially available, whereas the other propargyl group-containing scaffolds 2-5 [20][21][22][23] were synthesized from their hydroxyl precursors by simple alkylation reactions with propargyl bromide in the presence of sodium hydride as a base. The 2-azidoethyl glycosides were synthesized as shown in Schemes 1-3.…”

Synthesis of dimeric analogs of adenophostin A that potently evoke Ca2+release through IP3receptors

“…The linkers 14a–d were synthesized by slightly modifying previously reported procedures. 20 The oligoethylene glycols were first co-evaporated with toluene and then treated with sodium hydride in the presence of excess propargyl bromide to get dipropargyl polyethylene glycols 14a–d in good to excellent yields. The azide 13 was synthesized from glucose and xylose by several protection–deprotection reactions followed by phosphorylation as reported earlier.…”

Selected synthetic strategies to cyclophanes

“…[2 + 2 + 2] Co-trimerization: In 2003, Tanaka and Shirasaka [ 176 ] have reported a one-step synthesis of [6]metacyclophane 273 by a [2 + 2 + 2] co-trimerization of two different alkynes with a high chemo- and regioselectivity. The Rh(I)/H8-BINAP complex catalyzed the partially intermolecular cyclotrimerization of 1,9-decadiyne ( 271 ) and diethyl acetylenedicarboxylate ( 272 ) to give [6]metacyclophane derivative 273 ( Scheme 44 ) [ 177 ]. This approach is also applicable to synthesize various polyether-based cyclophanes.…”