UNSATURATED PHOSPHONATES AS ACYCLIC NUCLEOTIDE ANALOGS - ANOMALOUS MICHAELIS-ARBUZOV AND MICHAELIS-BECKER REACTIONS WITH MULTIPLE BOND SYSTEMS

Reaction of adenallene (4a) with methanesulfonyl chloride in pyridine afforded 4'-chloro-4'-deoxyadenallene (6a). A similar reaction with toluene-4-sulfonyl chloride (NEt3, CH2Cl2) led to elimination of the unsaturated moiety and formation of N9-(4-toluenesulfonyl)adenine (8a). Michaelis-Arbuzov reaction of E- and Z-unsaturated chlorides 13a and 16b with triethyl phosphite afforded phosphonates 14a and 17b. Dealkylation of the latter products, coupled in case of 17b with acid hydrolysis, led to phosphonic acids 15a and 18. By contrast, Michaelis-Arbuzov reaction with butynyl chlorides 19a and 19b led to elimination of unsaturated moiety and alkylation of the released heterocyclic bases to give N9-ethyl derivatives 20a and 20b. In the presence of iodide ion, N9-(2,3-butadien-1-yl)adenine (30a, from 19a) and/or unsaturated diphosphonates 25a and 25b were obtained. The Michaelis-Arbuzov reaction of chloroallene 6a led to 2'-phosphonate 33a which, after dealkylation, afforded phosphonic acid 35a. When iodide ion was present, both 2'- and 4'-phosphonates 33a and 36a were obtained. Compound 36a was also prepared by Michaelis-Becker reaction of chloroallene 6a with sodium diethyl phosphite in THF-HMPA. In DMSO, both phosphonates 33a and 36a were formed. Under similar conditions (DMF), chlorobutyne 19a gave 4'-phosphonate 36a. Dealkylation of 36a furnished phosphonic acid 37a. Adenallene (4a) and diethyl chlorophosphite in pyridine afforded phosphonate 33a whereas butynol 39a afforded only adenine (10a). The probable reaction course of these transformations and spectral properties of the reaction products will be discussed.