Jozef Hodyl PhD Thesis - Theses - Flinders University

XS HO O H61, n = 262, n = 3n+ClOSO63(1)Et 3 NDCMr.t.HOOOSn O64, n = 265, n = 3+ Et 3 NHCl(2)+K 2 CO 3HOOn66, n = 267, n = 3O+ potassium tosylateDMF80 0 CO68OH(3)H 2Pd/CDCMMeOHr.t.(4)HOOn69, n = 270, n = 3OH +O58OTsK 2 CO 3DMF50 0 COO+ potassium tosylatenO59 n = 260, n = 3OHScheme 2.6 Preparation of the hydroxy terminated polyether appended pendant arm epoxides 59 and60 with synthetic steps numbered in green.In step one it is apparent from the generic structure of parent polyethylene glycol(PEG) that substitution is possible at each hydroxy terminus. This is avoided 174 byproviding an excess of the appropriate PEG to optimise the formation of the monosubstitutedproducts in 81% yield for 64 and 76% yield for 65.It is well established that tosylates provide superior leaving ability to hydroxylgroups ensuring that nucleophilic attack from the deprotonated phenolic oxygen of 4-(benzyloxy)phenol, 68, would, in the following step, occur at the alpha carbon of themono-tosylated HTPEs 64 or 65. Thus the mono-benzyl-protected, hydroxyterminated di- or tri-ethylene glycol ether substituted hydroquinone derivatives, 66and 67, were obtained in four days with 68% yield for 66 and 72% yield for 67.Cleavage of the benzyl protecting group, Step 3, to gain p-HTPE substitutedphenols 69 and 70 was accomplished by hydrogenation of the benzyl protected44