title: Synthesis of all stereoisomers of sulfinylcalix[4]arenes.
abstract: All four stereoisomers of p-tert-butylsulfinylcalix[4]arene [4(rccc), 4(rcct), 4(rctt), and 4(rtct)], arising from the disposition of the four sulfinyl groups with respect to the mean plane of the four bridging sulfur atoms, have been prepared via oxidation of p-tert-butylthiacalix[4]arene (2) or its tetra-O-benzyl ethers 5 of defined conformations. Thus, treatment of 2 with 4.4 molar equiv of NaBO(3).4H(2)O gave the rtct and rctt isomers in 27% and 17% yields, respectively, while oxidation of cone 5 (5(C)) and partial cone 5 (5(PC)) proceeded stereoselectively to give, after debenzylation of the resulting tetrasulfoxides 12 and 15, the rccc and rcct isomers in 56% and 28% yields, respectively, based on 5. The sulfinylcalix[4]arenes 4 were treated with iodomethane in the presence of a base to give the corresponding tetramethyl ethers 16, the structures of which in regard to the disposition of the sulfinyl groups and the conformation of the phenol units were determined by X-ray crystallography. Also reported is the synthesis of all four conformational isomers of tetra-O-benzyl ether of 2 (5(C), 5(PC), 5(1,2-A), and 5(1,3-A)).
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan. n-moro@yz.yamagata-u.ac.jp
authors.forename: Naoya
authors.initials: N
authors.lastname: Morohashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Katagiri
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Iki
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yamane
authors.forename: Chizuko
authors.initials: C
authors.lastname: Kabuto
authors.forename: Tetsutaro
authors.initials: T
authors.lastname: Hattori
authors.forename: Sotaro
authors.initials: S
authors.lastname: Miyano