Todd has made highly significant contributions to the chemistry of natural products, in particular in relation to compounds which play important roles in biological systems. His researches on vitamins B
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, E and B
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were most elegant and have had far-reaching implications, but none more so than his structural and synthetic studies in the nucleic acid field. Here he developed methods for the synthesis of the nucleosides and for their phosphorylation; his work on the way they are combined made possible the subsequent determination of the three-dimensional structure of the nucleic acids thereby providing the basis for much of the exciting activity in the nucleotide field today. Todd’s achievements arise out of a rare combination of theoretical knowledge and outstanding experimental skill, with the most judicious exploitation of modern techniques. His work and his quality as an investigator have been widely recognized by biologists as well as by organic chemists.