We report here the syntheses and characterization of new crown‐type compounds 8 and 9 incorporated with one and two 4‐pyrone units. The reaction of compound 3 with 1,5‐bis(2‐hydroxyphenoxy)‐3‐oxapentane or catechol gave the desired molecules 8 and 9 in 65% and 25% yields, respectively. Compound 3 resulted from 1 by Wohl‐Ziegler bromination in small amounts and could be separated from five bromination by‐products by column chromatography. For example, 8 binds K+ and a pyrylium salt 11 (single crystal X‐ray structure analysis) can also be prepared starting from 3 by treatment of the latter with perchloric acid in the presence of acetonitrile.

Under basic conditions 2,6‐bis(bromomethyl)‐4‐pyrone 8 reacts with tetraethylene glycol to yield the unexpected macrocycle 9, which is related to the antibiotic Kjellmanianone 10. We propose that this ring transformation proceeds via the cyclopropyl intermediate d (Scheme 2), which undergoes a ring opening reaction comparable to the Favorskii rearrangement. Also, 8 reacts with methanol/sodium methoxide to yield the 3(2H)‐furanone derivative 11, the formation of which is suggested to proceed via the intermediate k with a carbenium‐oxonium‐ion subunit (Scheme 3). The structure of the 3(2H)‐furanone derivative was confirmed by X‐ray analysis.

Our aim to enlarge the ring of the crown type compound 1, using the two component dilution principle, leads to hitherto unknown macrocycles 6 and 7. J. Heterocyclic Chem., 38, 305 (2001).The synthesis is described according to Yamamoto et al. as follows [1]: The crown type compound 1 which is synthesized from 2,6-bis(bromomoethyl)-4-pyrone and 1,5-bis(hydroxyphenoxy)-3-oxapentane [2], was treated with phosphorous pentasulfide in benzene followed by an excess of methyl iodide to afford the corresponding pyrylium compound 3. This salt was hydrolyzed with potassium carbonate in aqueous methanol solution to give the ring-opened diketone 4. This diketone was without isolation desulfurized with Raney nickel in ethanol followed by aqeous titanium trichloride to provide the macrocyclus 5 and the diasteromeric diol 6. Compound 5 could not be isolated because a transformation to the cyclohexanone compound 7 takes place on account of an excess of potassium carbonate.Compound 6 is obtained as a 1:1 mixture of diastereomers as can be seen from the 13 C nmr spectrum, in which all signals are split into two lines. Interestingly, the 1 H nmr spectrum displays two signals for the OH protons at 2.87 and 3.12 ppm; one signal belonging to one diastereomer and the other to the second diastereomer.The constitution follows from DEPT-135 °C 13 C nmr spectrum. To determine the con-figuration at the cyclohexanone ring of compound 7, several NOE experiments were performed. Irradiation of H C causes signal enhancement of both H D and H B , but not H A . Therefore, H C must be equatorial. Irradiation of H D results in signal enhancement of H C and H B , but not of H A . The OH group is also equatorial. These results are only in accord with the depicted conformation, thus the compound 7 has the cis-configuration (O-Ar and OH D on the same side). EXPERIMENTALMelting points were determined on a Linström apparatus and are uncorrected. The uv spectrum was obtained on a HP 8451A Diode Array Spectrophotometer. The ir spectra were recorded on a Perkin-Elmer 297 spectrometer. The 1 H nmr and the 13 C nmr spectra were recorded on a Bruker AC 300 and a Bruker AVANCE CPX 400 spectrometer respectively. Mass spectra were obtained on a Finnigan MAT Bremen CH-7A spectrometer and Finnigan MAT Bremen CH-5DF. FAB spectra were determined on a CH-5-DF-MAT-Varian (80 eV). Elemental analyses were performed by the Institut für Pharmazie Analytical Service Laboratory. To crown type compound 1 [1] (2 g, 4.873 mmoles) in dry benzene (100 ml) phosphorous pentasulfide (1.12 g, 5.06 mmoles) was added, and the mixture was heated to reflux for 1 hour. After cooling the mixture was filtered and the solution was removed by evaporation at room temperature. The residue was purified by column chromatography (silica gel, ethyl acetate). Pure fractions were combined and concentrated. Red crystals were obtained from ethyl acetate/n-hexane, yield 1.

The preparation of novel crown type compounds 6 and 8 with a 4‐pyrone unit is described.