It consists of a phenanthrene ring fused with a cyclopentane ring. The monoclinic crystals are not isomorphic to cyclopentane. It is a fivefold geminal diol on a cyclopentane backbone. It can be synthesized from a cyclopentane derivative. The D ring has a cyclopentane structure. The formula of umbellulone is CHO, containing a cyclopropane and cyclopentane ring. They contain four cycloalkane ring structures, three cyclohexane rings and one cyclopentane ring. It has a strained ring system with a cyclopentane ring fused to a cyclopropane ring. Nye is also the exclusive global reseller of Pennzane multiplyalkylated cyclopentane fluids, oils and greases. Examples include ethane, 2-methylbutane, and cyclopentane (Moore, Stanitski, and Jurs 335). These cyclopentane rings can exist in tetraether lipids or diether lipids. Changing the cyclopentane ring to a pyrrolidine ring showed high inhibitory activity as well. Containing five silicon atoms arranged in a ring, it is the silicon analog of cyclopentane. Usually, a mixture of n-, i-, and increasingly cyclopentane is used for this purpose. This forms a cyclopentane ring in roughly the middle of the fatty acid chain.