Oxidative Fragmentations of the 5-alpha and 5-beta-Hydroxy-B-norcholestan-3-beta-yl Acetates
Authorized Users Only
2003
Authors
Bjelaković, Mira
Lorenc, Ljubinka
Pavlović, Vladimir D.
Tinant, Bernard
Declercq, Jean-Paul
Kalvoda, Jaroslav
Article (Published version)

Metadata
Show full item recordAbstract
Oxidations of 5α‐hydroxy‐B‐norcholestan‐3β‐yl acetate (8) with Pb(OAc)4 under thermal or photolytic conditions or in the presence of iodine afforded only complex mixtures of compounds. However, the HgO/I2 version of the hypoiodite reaction gave as the primary products the stereoisomeric (Z)‐ and (E)‐1(10)‐unsaturated 5,10‐seco B‐nor‐derivatives 10 and 11, and the stereoisomeric (5R,10R)‐ and (5S,10S)‐acetals 14 and 15 (Scheme 4). Further reaction of these compounds under conditions of their formation afforded, in addition, the A‐nor 1,5‐cyclization products 13 and 16 (from 10) and 12 (from 11) (see also Scheme 6) and the 6‐iodo‐5,6‐secolactones 17 and 19 (from 14 and 15, resp.) and 4‐iodo‐4,5‐secolactone 18 (from 15) (see also Scheme 7). Oxidations of 5β‐hydroxy‐B‐norcholestan‐3β‐yl acetate (9) with both hypoiodite‐forming reagents (Pb(OAc)4/I2 and HgO/I2) proceeded similarly to the HgO/I2 reaction of the corresponding 5α‐hydroxy analogue 8. Photolytic Pb(OAc)4 oxidation of 9 afforded,... in addition to the (Z)‐ and (E)‐5,10‐seco 1(10)‐unsaturated ketones 10 and 11, their isomeric 5,10‐seco 10(19)‐unsaturated ketone 22, the acetal 5‐acetate 21, and 5β,19‐epoxy derivative 23 (Scheme 9). Exceptionally, in the thermal Pb(OAc)4 oxidation of 9, the 5,10‐seco ketones 10, 11, and 22 were not formed, the only reaction being the stereoselective formation of the 5,10‐ethers with the β‐oriented epoxy bridge, i.e. the (10R)‐enol ether 20 and (5S,10R)‐acetal 5‐acetate 21 (Scheme 8). Possible mechanistic interpretations of the above transformations are discussed.
Keywords:
Oxidation / Lead-tetracetate / Steroids / Fragmentation / Isomers / Pb(OAc)4 / ConformationSource:
Helvetica Chimica Acta, 2003, 86, 6, 2121-2135Publisher:
- Wiley
Collections
Institution/Community
IHTMTY - JOUR AU - Bjelaković, Mira AU - Lorenc, Ljubinka AU - Pavlović, Vladimir D. AU - Tinant, Bernard AU - Declercq, Jean-Paul AU - Kalvoda, Jaroslav PY - 2003 UR - https://cer.ihtm.bg.ac.rs/handle/123456789/4187 AB - Oxidations of 5α‐hydroxy‐B‐norcholestan‐3β‐yl acetate (8) with Pb(OAc)4 under thermal or photolytic conditions or in the presence of iodine afforded only complex mixtures of compounds. However, the HgO/I2 version of the hypoiodite reaction gave as the primary products the stereoisomeric (Z)‐ and (E)‐1(10)‐unsaturated 5,10‐seco B‐nor‐derivatives 10 and 11, and the stereoisomeric (5R,10R)‐ and (5S,10S)‐acetals 14 and 15 (Scheme 4). Further reaction of these compounds under conditions of their formation afforded, in addition, the A‐nor 1,5‐cyclization products 13 and 16 (from 10) and 12 (from 11) (see also Scheme 6) and the 6‐iodo‐5,6‐secolactones 17 and 19 (from 14 and 15, resp.) and 4‐iodo‐4,5‐secolactone 18 (from 15) (see also Scheme 7). Oxidations of 5β‐hydroxy‐B‐norcholestan‐3β‐yl acetate (9) with both hypoiodite‐forming reagents (Pb(OAc)4/I2 and HgO/I2) proceeded similarly to the HgO/I2 reaction of the corresponding 5α‐hydroxy analogue 8. Photolytic Pb(OAc)4 oxidation of 9 afforded, in addition to the (Z)‐ and (E)‐5,10‐seco 1(10)‐unsaturated ketones 10 and 11, their isomeric 5,10‐seco 10(19)‐unsaturated ketone 22, the acetal 5‐acetate 21, and 5β,19‐epoxy derivative 23 (Scheme 9). Exceptionally, in the thermal Pb(OAc)4 oxidation of 9, the 5,10‐seco ketones 10, 11, and 22 were not formed, the only reaction being the stereoselective formation of the 5,10‐ethers with the β‐oriented epoxy bridge, i.e. the (10R)‐enol ether 20 and (5S,10R)‐acetal 5‐acetate 21 (Scheme 8). Possible mechanistic interpretations of the above transformations are discussed. PB - Wiley T2 - Helvetica Chimica Acta T1 - Oxidative Fragmentations of the 5-alpha and 5-beta-Hydroxy-B-norcholestan-3-beta-yl Acetates VL - 86 IS - 6 SP - 2121 EP - 2135 DO - 10.1002/hlca.200390169 ER -
@article{ author = "Bjelaković, Mira and Lorenc, Ljubinka and Pavlović, Vladimir D. and Tinant, Bernard and Declercq, Jean-Paul and Kalvoda, Jaroslav", year = "2003", abstract = "Oxidations of 5α‐hydroxy‐B‐norcholestan‐3β‐yl acetate (8) with Pb(OAc)4 under thermal or photolytic conditions or in the presence of iodine afforded only complex mixtures of compounds. However, the HgO/I2 version of the hypoiodite reaction gave as the primary products the stereoisomeric (Z)‐ and (E)‐1(10)‐unsaturated 5,10‐seco B‐nor‐derivatives 10 and 11, and the stereoisomeric (5R,10R)‐ and (5S,10S)‐acetals 14 and 15 (Scheme 4). Further reaction of these compounds under conditions of their formation afforded, in addition, the A‐nor 1,5‐cyclization products 13 and 16 (from 10) and 12 (from 11) (see also Scheme 6) and the 6‐iodo‐5,6‐secolactones 17 and 19 (from 14 and 15, resp.) and 4‐iodo‐4,5‐secolactone 18 (from 15) (see also Scheme 7). Oxidations of 5β‐hydroxy‐B‐norcholestan‐3β‐yl acetate (9) with both hypoiodite‐forming reagents (Pb(OAc)4/I2 and HgO/I2) proceeded similarly to the HgO/I2 reaction of the corresponding 5α‐hydroxy analogue 8. Photolytic Pb(OAc)4 oxidation of 9 afforded, in addition to the (Z)‐ and (E)‐5,10‐seco 1(10)‐unsaturated ketones 10 and 11, their isomeric 5,10‐seco 10(19)‐unsaturated ketone 22, the acetal 5‐acetate 21, and 5β,19‐epoxy derivative 23 (Scheme 9). Exceptionally, in the thermal Pb(OAc)4 oxidation of 9, the 5,10‐seco ketones 10, 11, and 22 were not formed, the only reaction being the stereoselective formation of the 5,10‐ethers with the β‐oriented epoxy bridge, i.e. the (10R)‐enol ether 20 and (5S,10R)‐acetal 5‐acetate 21 (Scheme 8). Possible mechanistic interpretations of the above transformations are discussed.", publisher = "Wiley", journal = "Helvetica Chimica Acta", title = "Oxidative Fragmentations of the 5-alpha and 5-beta-Hydroxy-B-norcholestan-3-beta-yl Acetates", volume = "86", number = "6", pages = "2121-2135", doi = "10.1002/hlca.200390169" }
Bjelaković, M., Lorenc, L., Pavlović, Vladimir D., Tinant, B., Declercq, J.,& Kalvoda, J.. (2003). Oxidative Fragmentations of the 5-alpha and 5-beta-Hydroxy-B-norcholestan-3-beta-yl Acetates. in Helvetica Chimica Acta Wiley., 86(6), 2121-2135. https://doi.org/10.1002/hlca.200390169
Bjelaković M, Lorenc L, Pavlović V, Tinant B, Declercq J, Kalvoda J. Oxidative Fragmentations of the 5-alpha and 5-beta-Hydroxy-B-norcholestan-3-beta-yl Acetates. in Helvetica Chimica Acta. 2003;86(6):2121-2135. doi:10.1002/hlca.200390169 .
Bjelaković, Mira, Lorenc, Ljubinka, Pavlović, Vladimir D., Tinant, Bernard, Declercq, Jean-Paul, Kalvoda, Jaroslav, "Oxidative Fragmentations of the 5-alpha and 5-beta-Hydroxy-B-norcholestan-3-beta-yl Acetates" in Helvetica Chimica Acta, 86, no. 6 (2003):2121-2135, https://doi.org/10.1002/hlca.200390169 . .