Ableitung von fettlöslichem Riboflavin

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Chemie: Veresterung

Vorsicht: Hautkontakt vermeiden. Handschuhe tragen:

40px-Hazard_X.svg.png Fettlösliches Riboflavin könnte über die Haut aufgenommen werden und dort als Photosensibilisator wirken.

Edwards, Saldano, Bueno, Silva, Alegria (2000)

Paper.svg Edwards, Saldano, Bueno, Silva, Alegria (2000)
Spectroscopic properties of hydrophobic Flavin esters: A one and two-dimensional 1H-NMR and 13C-NMR study
PubMed (title) PubMed (ID) Google Vorlage:Paper
RF 2',3',4’',5'-tetraacetate (RTA), RF tetrapropionate (RTP), RF tetrabutyrate (RTB)
and RF tetrapalmitate (RTPa) were synthesized according to the procedure described
by Ogasawara et al., modified increasing the reaction time and the temperature
with the length of the alkyl chain, from 30 min and 40ºC in the original work
to 3 hours for RTA up to 2 weeks at 65ºC for RTPa. Briefly, for each ester,
RF was added to a beaker containing a 1:1 mixture of the corresponding
(acetic, propionic, butyric or palmitic) acid and anhydride. After a dropwise addition
of 70% perchloric acid, the mixture was stirred during the adequate time and temperature
(see above). The mixture was cooled in an ice bath and diluted with an equal volume of
water, and the solution was then extracted three times with chloroform. The combined
chloroform extracts were washed four times with deionized water, followed with an
extraction with a saturated solution of NaCl. The solution was evaporated to dryness
and the product was then recrystallized from 95% ethanol.

Also einfach Säure dazu, Anhydrid dazu, Wasser wenn möglich entziehen, kochen und fertig. Die organische Säuren könnte auch aus einer Pflanzenöl-Verseifung stammen, die wären dann auch gleich ungesättigt und könnten evtl. polymerisieren. Allerdings geben die Autoren schon bei Palmitinsäure eine sehr geringe Ausbeute an (max. 8% gegenüber >70% bei Essigsäure), sodass ich davon ersteinmal Abstand nehme.

Ogasawara, Wang, Bobbitt (1992): Tetraacetylriboflavin

Paper.svg Ogasawara, Wang, Bobbitt (1992)
Dynamically Modified, Biospecific Optical Fiber Sensor for Riboflavin Binding Protein Based on Hydrophobically Associated 3-Octylriboflavin
PubMed (title) PubMed (ID) Google Vorlage:Paper
Preparation of 2’,3’,4’,5’-Tetraacetylriboflavin: A 5.0-g
sample of riboflavin was added to a 400-mL beaker containing
200 mL of a 1:1 (v:v) mixture of glacial acetic acid and acetic
anhydride. After the dropwise addition of 1 mL of 70% per-
chloric acid, the mixture was stirred for 30 min at 40 °C. The
mixture was cooled in an ice bath and diluted with an equal
volume of water, and the solution was then extracted three times
with 25 mL of chloroform. The combined chloroform extracts
were washed four times with 25 mL of deionized water followed
with a 25-mL extraction with a saturated solution of NaC1. The
solution was evaporated to dryness and the product was then
recrystallized from 95% ethanol producing a product with a
melting point of 238-239 °C.

Wheeler (1961)

5.0 grams of riboflavin, 20.0 cm^3 of acetic anhydride
and 100.0 cm^3 of pyridine were heated together in an
Erlenmeyer flask for a short time until all riboflavin
had dissolved. The solvent was then removed by heating
under vacuum. The residue was dissolved in a small
amount of pyridine, filtered and to the hot filtrate 200 cm^3
of water was added. After chilling small yellow needle
crystals formed which were removed by filtration. The
crystals were dried in a vacuum desiccator over sulfuric
acid. The yield was 5,78 grams (80% yield) of ribo-
flavin tetra-acetate which had an uncorrected melting
point of 237°-238°. The melting point of riboflavin tetra-
acetate is normally given as 238°-239°. The crystals were
very soluble in chloroform, pyridine and acetone; almost
insoluble in dioxane, ether, benzene and petroleum ether;
and soluble in boiling alcohol, xylene and ethyl acetate.
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