Synthesis of (+)-2R,3R,11R,12R- and (−)-2S,3S,11S,12S-tetraphenyl-18-crown-6

The synthesis of the title crown ethers starting from optically active hydrobenzoins is described. R(+)-1,in CDCl₃ ,preferentially extracts R(+)-phenylglycine methyl ester hydroperchlorate from an aqueous solution of the racemate with a chiral recognition factor of 1.5 as shown by nmr measurements.     

The structure of a 1:4 adduct between 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6) and thiourea

The structure of 18-crown-6·4 thiourea has been determined by single crystal X-ray methods. The unit cell is monoclinic and the space group isP2₁, witha=9.251(3),b=19.285(8),c=16.556(7) Å and =90.85(6)°. There are two formula units, C₁₂H₂₄O₆·4CH₄N₂S, in the asymmetric unit; finalR=0.086. One thiourea is attached at either side of the macrocycle (biangular conformation) via N–N...O bonds and the patterns in the two crystallographically-independent adductsA andB differ slightly, involving two bifurcated hydrogen bonds inA. Core adducts are linked by additional thiourea molecules via N–H...S bonds. As compared to the analogous 18-crown-6·5 urea, the present 1:4 stoichiometry might be attributed to the longer S...N hydrogen bonding distance, i.e., to the bigger van der Waals radius of sulphur. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82004 (31 pages). To obtain copies, see p. ii of this issue.     

(2R，3R)-和(2S，3S)-2-(4-羟基-3-甲氧基)-3-羟甲基-1，4-苯并二氧六环-6-醛的对映选择性合成

1,4-苯并二氧六环木脂素类天然产物多数具有增加胆碱乙酰化酶和抗肝毒等活性 ,其活性主要源于 1 ,4-苯并二氧六环官能团 [1] . 1 ,4-苯并二氧六环木脂素的消旋全合成已有报道 [2 ] ,但其不对称合成还是空白[3] .我们发展了一条对映选择性合成 1 ,4-苯并二氧六环木脂素的简捷有效的路线 .基于前面的工作 [4 ] ,我们发现 1 ,4-苯并二氧六环醛类衍生物是合成此类天然产物的关键中间体 ,选择 2 - (4-羟基- 3-甲氧基 ) - 3-羟甲基 - 1 ,4-苯并二氧六环 - 6-醛 (1 )作为目标分子 ,其合成路线如下 :Reagents and conditions:( ) Me OH,H2 SO4,9…