| Abstract
| - 2-(4-Nitrophenyl)ethylmethylenebis(phosphonate) (6) was prepared by reactionof equimolaramounts of 2-(4-nitrophenyl)ethyl alcohol andmethylenebis(phosphonyl) tetrachloride in thepresence of tetrazole. Compound 6 was further convertedinto the corresponding 4-nitrophenylethyltrisanhydride intermediate 7 by dehydration withdiisopropylcarbodiimide (DIC). Reaction of7with either 2‘,3‘-O-isopropylideneadenosine (8a)or 2‘,3‘-O-isopropylideneguanosine (8b)afforded,after hydrolysis, the desiredP1-[2-(4-nitrophenyl)ethyl]-P2-(2‘,3‘-O-isopropylideneadenosin-5‘-yl)methylenebis(phosphonate) (9a) and guanosine analogue9b, respectively. A similar treatment ofintermediate 7 with 3‘-O-acetylthymidine(12a),3‘-O-acetyl-2‘-deoxy-N4-benzoylcytidine(12b), 3‘-O-acetyl-2‘-deoxy-N6-benzoyladenosine(12c), and3‘-O-acetyl-2‘-deoxy-N2-isobutyrylguanosine(12d)gave the corresponding 2-(4-nitrophenyl)ethylmethylenebis(phosphonate)s 13a−d.These compounds as well as 9a,b were treated with1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) whichcausedelimination of the 2-(4-nitrophenyl)ethyl group. The baselabile 3‘-O-acetyl, N4-acetyl,N6-benzoyl,and N2-isobutyryl groups of12a−d were also removed during the DBUtreatment. Thus, the 5‘-methylenebis(phosphonate)s of2‘,3‘-O-isopropylideneadenosine (10a),2‘,3‘-O-isopropylideneguanosine (10b), thymidine (14a), 2‘-deoxycytidine(14b), 2‘-deoxyadenosine (14c), and2‘-deoxyguanosine (14d) were prepared in good yield.De-O-isopropylidenation of 10a and10b affordedadenosine 5‘-methylenebis(phosphonate) (11a) andguanosine 5‘-methylenebis(phosphonate)(11b),respectively.
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