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3.1. Synthesis of ent-17β-estradiol (i have no clue what any of this means)

Indenone 4 [33], the C,D-ring synthon, was treated with NaH in ethylene glycol dimethyl ether and reacted with tosylate 5b [29] to afford compound 6 (60%).
Hydrogenation of compound 6 gave a 52% yield of the indenones 7a (major isomer) and 7b (minor isomer).
Treatment of compound 7a with 10 N HCl at 0 °C results in epimerization of the (methoxyphenyl)ethyl group to give 7b and subsequent cyclization leads to Δ9(11) ent- steroid 8a (72%) and a small amount of the isomeric Δ8 ent-steroid 8b as products.
Under these reaction conditions, compound 7b also yields products 8a and 8b.
The trans ring fusion of the C,D-rings of ent-steroid 8a was established initially by 1H NMR and 13C NMR spectroscopy.
The chemical shifts of the 18-Me group protons (δ = 0.78) and the carbon resonance of this group (δ = 11.55) are both characteristic of the trans C,D-ring fusion of ent-steroid 8a [34].
Hydrogenation of compound 8a produced ent-steroids 9a (81%, major product) and 9b (minor product).
Removal of the tert-butyl protecting group from the oxygen atom at C17 using 6 N HCl in THF/EtOH converts compound 9a to ent-steroid 10, which was used without purification.
Removal of the methyl protecting group from the oxygen atom at C3 using DIBALH [35] converts compound 10 to ent-17β-estradiol 3 (84% yield overall for the 9a to 3 conversion).
Alternatively, methyl group removal from the oxygen atom at C3 using 48% HBr [36] in glacial acetic acid gave a mixture of ent-steroids 3 (minor product) and 11 (major product).
The overall yield for the conversion of indenone 4 to ent-17β-estadiol is 15.2%

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