Five-membered ring systems oxazolidines

Most of the reactions involving nucleophilic attack at a carbon atom of the ring result in cleavage of the five-membered ring system (which is in most cases either an oxazolidine or an oxazolidinone). Basic hydrolysis of... 

Cycloneosamandione is an isomer of samandarone but differs characteristically by the absence of the oxazolidine system. The IR-spectrum proves that one oxygen atom belongs to a carbonyl groujj in a five-membered ring. The second one belongs to an aldehyde-ammonia group which can react in two tautomeric forms ... 

Another alkaloid with the oxazolidine system is samandaridine (XVII), C21H31NO3, also a secondary amine. Chemical reactions (9) and IR-spectra indicate that it possesses a five-membered lactone ring. Its structure was also elucidated by X-ray analysis. Samandaridine hydrobromide crystallizes from methanol in monoclinic prisms its space group is C2 with four molecules in the unit cell. The cell constants are a = 14.50 A, b = 6.15 A, c = 22.52 A, = 94° (10). 

A second alkaloid without the oxazolidine ring, but with the carbino-lamine system is cycloneosamandaridine (XXVII). The IR-spectrum evidences a five-membered lactone ring (band at 1780 cm i) as well as the carbinolamine group (bands at 1050/1180 cm i). The IR-spectrum of the X-acetyl compound no longer shows these hands at 1050-1180 cm i, hut an additional carbonyl frequency at 1735 cm i for an aldehyde group. The mass spectrum confirms the molecular formula as well as structure XXVII(id). 

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