Draft:Filsuvez

Introduction
Filsuvez, also known by the former name Oleogel-S10, is a medicine used for the treatment of wounds associated with the skin conditions epidermolysis bullosa. The active substance, which is ‘Birch Triterpenes’, in this gel is extracted from birch bark. It consists of two species of birch bark, including betulin, betulinic acid, lupeol, erythrodiol and oleanolic acid. Filsuvez can cause hypersensitivity reactions on the application.

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Structure
The most common birch triterpenes in Filsuvez is betulin which has 5 rings in the skeletal structure making it part of pentacyclic triterpenoids. Betulin is lupane and has a role as metabolite, antiviral agent, analgesic, anti-inflammatory agent and antineoplastic agent. Betulin is very soluble in diethyl ether, ethyl acetate and hardly soluble in ethanol and benzene.

The chemical name of the most occurring birch triterpenes betulin is (1R,3aS,5aR,5bR,7aR,9S,11aR,11bR,13aR,13bR)-3a-(hydroxymethyl)-5a,5b,8,8,11a-pentamethyl-1-(prop-1-en-2-yl)-icosahydro-1H-cyclopenta[a]chrysen-9-ol.

Reactivity
Betulin can react with sulfamic acid and ammonium sulfamate to botulin sulfamate under presence of 6 catalysts: Amberlyst-15®, Sibunit (granules) oxidized at 500 °C, Sibunit (powder) oxidized at 400 °C, Sibunit-sulfated, TiO2, and ɣ-Al2O3 with Amberlyst-15® being the main catalyst. The use of sulfamic acid with Amberlyst-15® leads to only betulin sulfates, while the use of ammonium sulfamate with Amberlyst-15® also creates other betulin derivatives besides botulin sulfates. X-ray has shown that sulfation of betulin causes stronger amorphization of the sulfates.

Synthesis
Birch triterpenes is synthesized out of Acetyl-CoA which is a product of decarboxylation of pyruvate and also a main molecule in the Krebs cycle. HMG-CoA is synthesized from Acetyl-coa under catalyses of hmg-coa synthase. After this, the HMG-Coa is irreversibly reduced by HMG-Coa reductase to mevalonic acid. The synthesized mevalonic acid is then phosphorylated and decarboxylated to produce IPP. The IPP can react with isomerases to form the isomer DMAPP. IPP and DMAPP are then condensed to form FPP under catalysation of FPP synthase. Then two molecules of FPP are used as substrate by squalene synthase to form squalene. Squalene is then oxidized into 2,3-oxidosqualene by squalene epoxidase. After this lupeol, the precursor of betulin, is synthesized by poly-cyclization creating the ring structures of lupeol with the help of lupeol synthase. Lastly, cytochrome enzyme P450 oxidates the methyl group at the C-28 carbon of lupeol to form betulin.