Yy-Dimethylallyl

Ergot Alkaloids.—4-(yy-Dimethylallyl)tryptophan (122) is the first intermediate beyond tryptophan in ergot alkaloid biosynthesis. Chanoclavine-I (127) is the first tricyclic base (cf. Vol. 10, p. 26, and ref. 2). Recently, (124 labels as shown) has been found to be a very efficient and intact precursor for elymoclavine (128).45 The high level of incorporation indicates that (123) is a probable intermediate situated between (122) and (127). The decarboxylation product (125) was not utilized for biosynthesis, so, although decarboxylation of (123) is required for the conversion of (123) into (127), either it is intimately associated with ring-closure or an imine that is related to (126) is involved. 

Important variants of procedure have been tested, providing wider possibilities for thio-Claisen rearrangements in synthesis like any other method for forming carbon-carbon bonds whose scope exceeds its limitations, there is the likelihood of studies of the type described in this Section being taken up in many more laboratories. Lithiation of allyl sulphides is followed by rearrangement, providing a very efficient method for the synthesis of thiols, alkyl sulphides, and hydrocarbons of the squalene type, or based upon the artemisyl skeleton. Typically, benzyl yy-dimethylallyl sulphide (65) gives (66) with four equivalents of... 

---