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In this lecture, an account is presented of the high points in the progress towards the synthesis of vitamin B 12 made during 1968-1970 in the collaborative programme carried out at the Eidgenössische Technische Hochschule in Zürich andin Cambridge at Harvard, under the leadership of Albert Eschenmoser and the lecturer. The point of furthest advance is represented by the obtention by total synthesis of heptamethyl bisnorcobyrinate (IX), which has been found to be identical with a sample of natural provenance. It is my privilege this morning to act as spokesman for two groups of investigators, in Zürich and in Cambridge, associated with Professor Albert Eschenmaser and myself, one of whose aims it is to effect the synthesis of vitamin B 12 • Of the results of this very wide-ranging collaborative investigation, only a portion can be presented here, and the choice I have made is to portray the present state of the work insofar as it relates directly to the establishment of a synthetic path to the vitamin. The next previous International Symposium on the Chemistry of Natural Products, held in London in 1968, adopted as its symbol a device cf. (I) which MeOOC MeOOC (I) 283 OOMe COOMe COOMe Ju
R. B. Woodward (Fri,) studied this question.