Noun
English Wikipedia has an article on:thiazolidineWikipedia
thiazolidine (countable and uncountable, plural thiazolidines)
(organic chemistry) A saturated, five-membered heterocycle containing three carbon atoms and a sulfur and nitrogen atom in the 1,3 positions; any derivative of this compound
The image shows that the thiazolidine ring and fused four-membered β-lactam are not in the same plane The term " penam " is used to describe the common core skeleton of a member of the penicillins. Source: Internet
The β-lactam ring is itself fused to a five-membered thiazolidine ring. Source: Internet