SYNTHESIS OF 2-SUBSTITUTED ESTERS OF ASCORBIC ACID USING 5,6-O-ISOPROPYLIDENE-L-ASCORBIC ACID
Sonjiala Hotchkiss, Samantha Barrera, Fernando De La Torre, Jose Rizo, Naquiba Williams, Adam Abdi, Akinyemi Olowu, Alberto Palacios, Edward Alexander, Emmanuel Gutierrez.
San Diego Mesa College, San Diego, CA.
Ascorbic acid (AA) or vitamin C is a powerful antioxidant important to the healthy functioning of many plants and animals. In addition, AA is effective at suppressing growth of cancerous tumors due to its ability to inhibit the glycolytic enzymes phosphofructokinase -1 (PFK-1) and lactate dehydrogenase (LDH). Further research has shown that 6-substituted and 2,6-disubstituted fatty acid derivatives of AA inhibit PFK-1 and LDH at a greater rate than AA. Preparation of the 2-monosubstituted derivatives of AA is of special interest because it will elucidate whether its antioxidant activity affects inhibition of PFK-1 and LDH. Research has shown that 2-substituted derivatives have significantly less antioxidant activity than either 6-substituted esters or 2,6-disubstituted esters of AA, and may have mild proxidant activity. Our hypothesis was that the use of the 5,6-O-isopropylidene-L-ascorbic (IAA) method to produce AA-2-palmitate could be generalized to produce other 2-substituted monoesters of AA. This method included the synthesis of IAA using ascorbic acid, acetone, and acetyl chloride. IAA was then stirred at room temperature with a fatty acid acyl chloride in dry pyridine and dry acetone. After workup, the 2-substituted esters were recrystallized from a mixture of petroleum ether and chloroform. This method was used to synthesize ascorbic acid-2-palmitate, -2-laurate, and -2-caprylate. Thin layer chromatography, infrared spectroscopy, and nuclear magnetic resonance were used to confirm the production of the 2-monoesters of AA. A mechanism involving a carbanion intermediate is proposed for the formation of the 2-substituted esters of AA.