Sintesis 8-metoksi-6-propenil flavanon dari eugenol minyak daun cengkeh

KUSMIYATI, Prof. Dr. Sabirin Matsjeh

2008 | Tesis | S2 Ilmu Kimia

Telah dilakukan sintesis turunan flavanon dengan bahan dasar eugenol yang bertujuan untuk mengetahui pengaruh gugus allil. Sintesis ini meliputi beberapa tahap yaitu: isolasi eugenol, reaksi adisi eugenol dengan asam format, reaksi asetilasi eugenol dan 1-(4-hidroksi-3-metoksifenil)-2-propanil format menggunakan asetat anhidrida, reaksi penataan ulang Fries terhadap eugenil asetat dan 1-(4-asetoksi-3-metoksifenil)-2-propanil format, dan reaksi kondensasi 1-(2-hidroksi-3-metoksi-5-propenil)-asetofenon dengan benzaldehida. Isolasi eugenol dilakukan dengan penambahan basa NaOH. Reaksi adisi eugenol dengan asam format dilakukan dengan perbandingan eugenol:asam format = 1:27. Reaksi adisi ini dilakukan pada temperatur 130 ËšC selama 22 jam. Reaksi asetilasi pada eugenol dan1-(4-hidroksi-3-metoksifenil)-2-propanil format menggunakan pereaksi asetat anhidrida, katalis natrium asetat dalam pelarut dietil eter. Reaksi penataan ulang Fries terhadap eugenil asetat dan 1-(4-asetoksi-3- metoksifenil)-2-propanil format dilakukan dengan pemanasan menggunakan katalis AlCl3, pelarut diklorometana pada temperatur 120 ËšC selama 3 jam. Reaksi kondensasi dilakukan dengan mereaksikan hasil penatan ulang Fries menggunakan benzaldehida dengan katalis NaOH dalam pelarut etanol-air, disertai pengadukan selama 3 jam. Hasil isolasi dari minyak daun cengkeh menghasilkan eugenol dengan kemurnian 99,46% yang berupa cairan berwarna kuning kecoklatan. Gugus allil pada eugenol setelah mengalami adisi mengunakan asam format menghasilkan 1- (4-hidroksi-3-metoksifenil)-2-propanil format yang berupa cairan kuning dengan rendemen sebesar 31,22%. Reaksi asetilasi eugenol menghasilkan eugenil asetat yang berupa cairan berwarna kuning dengan rendemen 78,48%. Reaksi asetilasi 1- (4-hidroksi-3-metoksifenil)-2-propanil format menghasilkan 1-(4-asetoksi-3- metoksifenil)-2-propanil format berupa cairan kuning dan rendemennya sebesar 78,68%. Penataan ulang Fries terhadap eugenil asetat menghasilkan dimer dari eugenil asetat yang berupa cairan kental coklat kehitaman. Penataan ulang Fries tehadap 1-(4-asetoksi-3-metoksifenil)-2-propanil format menghasilkan 1-(2- hidroksi-3-metoksi-5-propenil)-asetofenon dengan hasil samping 1-(2-hidroksi-3- metoksi-5-propanil)-asetofenon, masing-masing kadarnya sebesar 43,26% dan 9,84%. Sintesis senyawa flavanon dilakukan dengan mereaksikan hasil penataan ulang Fries menggunakan benzaldehida. Hasil sintesis flavanon berupa cairan berwarna kuning, dimana setelah dipisahkan menggunakan KLT preparatif didapatkan senyawa 8-metoksi-6-propenil flavanon dan 8-metoksi-6-propanil flavanon, masing-masing dengan kadar sebesar 69,18% dan 30,82%.

The synthesis of one flavanone derivative, in order to study the influence of allilic substituent, has been done. The synthesis was carried out through several reactions, i.e. Isolation of eugenol, addition of formic acid to eugenol, acetylation reaction of eugenol and 1-(4-hydroxy-3-methoxyphenyl)-2-propanyl formate, Fries rearrangement reaction of eugenyl acetate and 1-(4-acetoxy-3- methoxyphenyl)-2-propanyl formate, and condensation reaction of 1-(2-hydroxy- 3-methoxy-5-propenyl)-acetophenone and benzaldehyde. Isolation of eugenol from clove leave oil was done using NaOH. Formic acid addition was performed using eugenol and formic acid in the mol ratio of =1:27 at 130 ËšC for 22 hours. Acetylation reaction of eugenol and 1-(4-hydroxy-3- methoxyphenyl)-2-propanyl formate was carried out using acetic acid anhidryde, sodium acetate as catalyst, and diethyl ether as the solvent. Meanwhile, Fries rearrangement of eugenyl acetate and 1-(4-acetoxy-3-methoxyphenyl)-2-propanyl formate was done by heating under AlCl3, dichloromethane as the catalyst and solvent, respectively. Condensation of Fries product with benzaldehyda was carried out through 3 hours stirring under NaOH catalysis in ethanol-water. Isolation of eugenol produced 99.46% of eugenol as light yellow oil. Addition of formic acid into allilic functional group of eugenol afforded 1-(4- hydroxy-3-methoxyphenyl)-2-propanyl formate as 31.22% of yellow oil. Acetylation reaction of eugenol gave 78.48% eugenyl acetate as yellow oil. Acetylation of 1-(4-hydroxy-3-methoxyphenyl)-2-propanyl formate produced 78,68% 1-(4-acetoxy-3-methoxyphenyl)-2-propanyl formate as yellow oil. Meanwhile Fries rearangement of eugenyl acetate yielded lightly brown oil of dimer. Fries rearrangement of 1-(4-acetoxy-3-methoxyphenyl)-2-propanyl formate produce 1-(2-hydroxy-3-methoxy-5-propenyl)-acetophenone and 1-(2- hydroxy-3-methoxy-5-propanyl)-acetophenone as side product 43.26% and 9.48%, respectively. Condensation between that Fries product and benzaldehyde yielded a mixture of 8-methoxy-6-propenyl flavanone and 8-methoxy-6-propanyl flavanone in the percentage of 69.18% and 30.82%, respectively.

Kata Kunci : eugenol, eugenil asetat, penataan ulang Fries, Flavanon, eugenyl acetate, Fries rearrangement, flavanone