A method for the preparative stepwise degradation of polyribonucleotides has resulted from the development of a new reaction sequence employing the periodate oxidation-/? elimination-dephosphorylati on procedure. The method consists of a series of degradation cycles each of which involves (i) the periodate oxidation of the 3'-terminal of the polynucleotide, (ii) the removal of the excess periodate by reaction with rhamnose, (iii) the cleavage of the oxidized terminal nucleoside from the chain and the enzymatic dephosphorylation of the polynucleotide product in one step, and (iv) the separation of the polynucleotide from the reactants and other products. The reaction sequence has a number of advantages over previously used procedures in which the periodate oxidation and the /3-elimination steps were usually combined in the one reaction mixture and the dephosphorylation was effected in a separate reaction. The conditions for quantitative reaction in each step of the degradation cycle have been perfected by using mononucleotides, dinu-

The ADP analogue in which the 5'-oxygen has been replaced by a methylene group can be prepared by condensing 5'-deoxy-5'-phosphonomethyladenosine with inorganic phosphate. This analogue readily polymerizes onto the primer A-A in the presence of the enzyme polynucleotide phosphorylase and either Mg2+ or Mn2+. The initial products are of the form A-A(-cA)n-cA (where "-" and "-c" stand for the normal phosphodiester linkage and the linkage in which the 5'-oxygen is replaced with the methylene group, respectively). Treatment of these with alkali yields adenosine 2'(3')-phosphate and the series (A(-cA)n-cA containing only phosphonomethylene linkages. The decamer A(-cA)8-cA interacts with two molecules of U(-U)8-U to form a triple-standard structure that has a stability similar to that exhibited by the analogous complex formed from A(-A)8-A and U(-U)8-U. This property, along with the resistance of these oligomer analogues toward nucleases that cleave phosphodiester linkages between the phosphorus and the 5'-oxygen, should provide a strong rationale for application of phosphonomethylene linkages in schemes for therapeutic drug design that use the antisense strategy.

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From the bark of Flindersia maculosa Lindl. were isolated the known alkaloids, kokusaginine and flindersiamine, the new alkaloids, maculine and maculosine, the known coumarin, collinin, and a triterpene, flindissol. Maculine appears to be a methylenedioxydiotamnine. The leaves contained kokusaginine, the new alkaloid, maculosidine, and the new flavone, flindulatin. The structure 6,s-dimethoxydictamnine is proposed for maculosidine, and flindulatin is shown by degradation and synthesis to be 5-hydroxy-3,4',7,8-tetramethoxyflavone (3,4',7,8-tetramethylherbacetin).

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