Chiral macrocyclic polyether diesters

The chiral dimethyl derivatives RR)-M and (SS)-84 of tetraethylene glycol have been employed (126) in the preparation of chiral macrocyclic polyether diesters such as (JU )-85 and (SS)S6. The reactions of the chiral diols with the appropriate diacid chlorides generally proceed (Scheme S) in good yield in warm benzene under high dilution conditions. 

The pyridine subcycle unit has been introduced into a wide range of 18-crown-6 derivatives. For example, reaction of 2,6-pyridinedicarbonyl chloride with the dimethyl substituted tetraethylene glycol (SS)-84, derived from (S)-lactic acid, afforded (126) the chiral macrocyclic polyether diester (5S)-184. A similar preparative approach (127) gave (SS)-185, where the source of the chirality is (5)-mandelic acid. 

The reaction sequence outlined in Scheme 12 illustrates how macrocyclic polyether-thiono diesters such as RR)-lfi6 can be prepared (184) from 0,0-dimethyl 2,6-pyridinedicaibothiolate and (RR)-S4, Potassium thiocyanate forms a 1 1 crystalline complex with (RR)-1S6 and presumably the potassium ion serves as a template for the (1 -I-1) cyclization. Raney nickel desulfurization of (/ R)-186 yields the chiral pyridino-18-crown-6 derivative RR)-191. 

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See also in sourсe #XX -- [ ]

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