Secosteroid

[1]

Cholecalciferol, an example of a 9,10-secosteroid. IUPAC-approved carbon numbering and ring labeling is shown in the picture. Since secosteroids are derived from steroids, they retain the same labeling system as steroids. [1]: §3S-8 
The parent steroid skeleton. The B-ring of the parent steroid is broken between C9 and C10 to yield D vitamins.

A secosteroid (/ˈsɛkoʊˌstɛrɔɪd/) is a type of steroid with a "broken" ring. The word secosteroid derives from the Latin verb secare meaning "to cut",[2]: 241  and 'steroid'. Secosteroids are described as a subclass of steroids under the IUPAC nomenclature.[1]: §3S-1 [3] Some sources instead describe them as compounds derived from steroids.[4]

Types or subclasses of secosteroids are defined by the carbon atoms of the parent steroid skeleton where the ring cleavage has taken place. For example, 9,10-secosteroids are derived from cleavage of the bond between carbon atoms C9 and C10 of the steroid B-ring (similarly 5,6-secosteroids, 13,14-secosteroids, etc.).[1]: §3S-8 

The prototypical secosteroid is cholecalciferol (vitamin D3).[5] Its IUPAC systematic is "(5Z,7E)-(3S)-9,10-secocholestra-5,7,10(19)-trien-3-ol".[1]: §3S-8 

Some nonsteroidal estrogens, like doisynolic acid (cleaved on the D ring)[6] and allenolic acid,[citation needed] are also secosteroids or secosteroid-like compounds.

  1. ^ a b c d e Moss GP and the Working Party of the IUPAC-IUB Joint Commission on Biochemical Nomenclature. "The Nomenclature of Steroids". Queen Mary University of London. also available as Moss GP (1989). "Nomenclature of Steroids (Recommendations 1989)". Pure Appl. Chem. 61 (10): 1786f. doi:10.1351/pac198961101783.
    1. a b c Chapters 3S-8 "Ring fission" and 3S-9 "Vitamin D group"
    2. ^ (esp. 3S-1.4, incl. note 4) "Steroids are compounds possessing the skeleton of cyclopenta[a]phenanthrene or a skeleton derived therefrom by one or more bond scissions or ring expansions or contractions."
  2. ^ Ayers D (1972). Bioscientific Terminology. Tucson: University of Arizona Press. ISBN 978-0-8165-0305-6.
  3. ^ Hill RA; Makin HL; Kirk DN; Murphy GM (1991). Dictionary of Steroids (1st ed.). London: Chapman & Hall. ISBN 978-0-412-27060-4.
  4. ^ "Definition of secosteroid". Farlex Partner Medical Dictionary. TheFreeDictionary.com. A compound derived from a steroid in which there has been a ring cleavage.
  5. ^ Hanson JR (2010). "Steroids: partial synthesis in medicinal chemistry". Nat Prod Rep. 27 (6): 887–99. doi:10.1039/c001262a. PMID 20424788.
  6. ^ Meyers, CY; Kolb, VM; Gass, GH; Rao, BR; Roos, CF; Dandliker, WB (October 1988). "Doisynolic-type acids--uterotropically potent estrogens which compete poorly with estradiol for cytosolic estradiol receptors". Journal of Steroid Biochemistry. 31 (4A): 393–404. doi:10.1016/0022-4731(88)90307-x. PMID 3172773.