We have synthesized a series of oligonucleotides containing the EcoRI (GAATTC) or EcoRV (GATATC) recognition site within which or adjacent to which thymidine was substituted by uridine or derivatives of uridine. The effects of these substitutions on the rate of the EcoRI and EcoRV catalyzed cleavage reaction were investigated. Our results show that most of the substitutions within the site are quite well tolerated by EcoRI, not, however, by EcoRV. We conclude that the thymin residues most likely are not directly involved in the recognition process of the EcoRI reaction. In contrast, they are major points of contact, between substrate and enzyme in the EcoRV reaction. The effects of substitutions in the position adjacent to the recognition site is also markedly different for EcoRI and EcoRV. Here, EcoRI seems to be considerably more selective than EcoRV.

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The antiviral activity of some α‐adamantyl carbonyl compounds of type (3) is greater than that of 1‐amino‐adamantane. Syntheses of the kind shown below are therefore of considerable interest.

The emergence of a simple translation device consisting of an assembler strand (primordial mRNA) and RNA hairpins (primordial tRNA) is presumed to be an important step leading to the origin of life. The assumption of a non-enzymatic interaction of primordial tRNA and mRNA is experimentally approached. DNA hairpins containing five or more adenosine residues in the loop are able to bind to complementary oligonucleotides covalently bound to cellulose. The exact number of base pairs formed between the hairpins and the assembler strand is determined by two methods applied to DNA hairpin/assembler complexes. The melting temperature of a complex is measured and the cleavage pattern by nuclease from mung bean is determined. The loop of the smallest hairpin able to bind consists of five adenosine residues and only three base pairs are formed. This supports the idea of a primordial recognition similar to the contemporary codon-anticodon interaction.The emergence of a simple translation device is a crucial step in the process leading to the origin of life. A proposed translation device [l] consists of interacting oligoribonucleotides. The occurrence of short oligoribonucleotides seems reasonable, since the synthesis of chemically activated ribonucleotides under almost primordial conditions [2], their oligomerisation [3] and their template-directed enzyme-free polymerisation [4, 51 have been demonstrated. The model for self-organisation of matter needs oligoribonucleotides with a hairpin structure acting as primeval tRNA and a singlestranded polynucleotide functioning as primeval mRNA. This single-stranded assembler is thought to bind the hairpin molecules by formation of three base pairs with the loop nucleosides thus arranging the hairpins in a distinct sequence. The base-pairing interactions are thought to be stabilized additionally by lateral forces between the helical parts of the hairpin oligonucleotides occurring at a high Mg2 + concentration. The search for conditions leading to stable binding of hairpins to single strands by base triplets is of interest and a presupposition for intended formation of the peptide bond.In order to investigate the proposed base-pairing ability, two sets of molecules containing either thymidine or deoxyadenosine in the loop region both with an identical helical region as shown in Fig. 1 were synthesized 16 size of the loop was varied with regard to a possible primordial codon-anticodon interaction. The binding ability of the hairpins to complementary homooligonucleotides chemically bound to a solid support was investigated. This method had been originally used for the study of complexes of singlestranded oligonucleotides [8, 91. In order to investigate the steric arrangement of the particular loop nucleosides in free and complexed hairpin oligonucleotides, the single-strandspecific nuclease from mung bean was used as a structural probe [lo, 111. The best known similar nuclease S1 from Aspergillus oryzae had been used as a structural tool to reveal special features of tRNA [12, 131. MAT...

Mono‐ and bicyclic as well as spirocyclic carbonyl compounds can be prepared by intramolecular tert‐alkylation of olefins such as (1) with SnCl4. An O‐stannyl derivative and a carbenium ion are probably intermediates in the reaction, which should find application in terpene and steroid syntheses.