Heterocycles containing an Oxygen Atom in each of

7 Heterocycles containing an Oxygen Atom in each of Two or More Rings 

The structures and absolute configurations of acetoxyeriobrucinol methyl ether (268 R = OAc) and of eriobrucinol methyl ether (268 R= H) have been studied by X-ray crystallography. Similar studies have been made on the halogenoacetates of (—)-bruceol (269 R = OCOCH2X) and ( )-deoxybruceol (269 R = H).  

There has been a slight decrease in the total number of papers and patents this year, due in particular to a slackening in the flood of patents concerned with benzo[l,4]diazepines and related systems that are of potential pharmacological value. However, interest in 1,2- and 1,3-diazepines and in oxepin chemistry continues to increase and there has been a welcome upswing in the number of papers concerned with systems containing three heteroatoms, although this is still an area with much unexplored territory. 

General reviews on carbenes and nitrenes in heterocyclic chemistry and on the synthesis of saturated heterocycles have been published this year, and also specific reviews on 1,2-diazepines, 1,2-benzodiazepines, thiepins, dithiepins, and aza-azulenes.  

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