Chemistry:Previtamin D3

Previtamin D₃

Names
IUPAC name (3S,6Z)-9,10-Secocholesta-5(10),6,8-trien-3-ol
Systematic IUPAC name (1S)-4-Methyl-3-[(Z)-2-{(1R,3aR,7aR)-7a-methyl-1-[(2R)-6-methylheptan-2-yl]-2,3,3a,6,7,7a-hexahydro-1H-inden-4-yl}ethen-1-yl]cyclohex-3-en-1-ol
Other names Previtamin D3
Identifiers
CAS Number	1173-13-3 Y 17592-07-3 Y
3D model (JSmol)	Interactive image
ChemSpider	78098 Y 4832524 (E)-en Y 9660762 (1S)-1-ol, (E)-en, (1R,7aR)-7a-meth,-1-hept, (2R)-2-yl Y 9375051 (1S)-1-ol, (Z)-en, (1R,7aR)-7a-meth,-1-hept, (2R)-2-yl Y
EC Number	241-561-3
MeSH	Previtamin+D(3)
PubChem CID	86590 6178113 (E)-en 25245851 (1S)-1-ol, (Z)-en, (2R)-2-yl 11485943 (1S)-1-ol, (E)-en, (1R,7aR)-7a-meth,-1-hept, (2R)-2-yl 11199982 (1S)-1-ol, (Z)-en, (1R,7aR)-7a-meth,-1-hept, (2R)-2-yl
UNII	HDA46400N5 Y 6RR0I9PK8W Y
InChI InChI=1S/C27H44O/c1-19(2)8-6-9-21(4)25-15-16-26-22(10-7-17-27(25,26)5)12-13-23-18-24(28)14-11-20(23)3/h10,12-13,19,21,24-26,28H,6-9,11,14-18H2,1-5H3 Y Key: YUGCAAVRZWBXEQ-UHFFFAOYSA-N Y
SMILES CC(C)CCCC(C)C1CCC2C(C=CC3=C(C)CCC(O)C3)=CCCC12C
Properties
Chemical formula	C27H44O
Molar mass	384.648 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Previtamin D₃ is an intermediate in the production of cholecalciferol (vitamin D₃).

It is formed by the action of UV light, most specifically UVB light of wavelengths between 295 and 300 nm, acting on 7-dehydrocholesterol in the epidermal layers of the skin.

The B ring of the steroid nucleus structure is broken open, making a secosteroid. This then undergoes spontaneous isomerization into cholecalciferol, the prohormone of the active form of vitamin D, calcitriol.

The synthesis of previtamin D₃ is blocked effectively by sunscreens.