5pregnan

5pregnan refers to a group of steroid compounds that share a common structural backbone. This backbone consists of 21 carbon atoms arranged in a characteristic fused ring system. The "pregnan" designation specifically indicates the presence of this C21 steroid nucleus.

These compounds are of significant biological importance, particularly as precursors and metabolites of steroid hormones. The most well-known examples within this class are progesterone and its derivatives. Progesterone, a crucial hormone in the female reproductive cycle, pregnancy, and embryogenesis, is a prime example of a 5pregnan derivative. Other related compounds include pregnenolone, which serves as an intermediate in the biosynthesis of many steroid hormones.

The 5pregnan structure is characterized by a D ring that is five-membered, fused to the C ring. The numbering of the carbon atoms is standardized, starting from the A ring and proceeding through the D ring. Modifications to this basic 5pregnan skeleton, such as the addition of hydroxyl groups, ketone functionalities, or unsaturation, lead to the diverse array of steroid hormones and related molecules found in biological systems. Understanding the 5pregnan structure is fundamental to comprehending steroid biochemistry and the physiological roles of these vital compounds.