On the methanolysis of KBBL, an immunostimulant derived from ascorbic acid

• Published in: Tetrahedron Vol. 49; no. 34; pp. 7437 - 7444
• Main Authors: Campbell, Erin, Newhouse, Bradley J, Bordner, Jon, Kleinman, Edward F
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 20.08.1993; Elsevier
• Subjects: ascorbic acid; butyrolactone; Chemistry; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Heterocyclic compounds; Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives; immunostimulant; KBBL; ketal; Organic chemistry; Organic compounds; Physics; Preparations and properties; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; KBBL; ascorbic acid; immunostimulant; butyrolactone; ketal; Molecular structure; Lactone; Acid catalysis; Hemiacetal; Methanolysis; Tricyclic compound; Experimental study; Oxygen heterocycle; X ray diffraction; Acetal; Immunostimulant agent; Ascorbic acid derivatives; Cyclization; Spirocyclization; Bicyclic compound; Organic compounds; Crystalline structure
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/S0040-4020(01)87220-3

Methanolysis of the immunostimulant KBBL ( 1a) was studied to provide new internal ketal derivatives for potential elaboration of the butyrolactone nucleus (derived from ascorbic acid). Treatment of the immunostimulant KBBL ( 1a) in dry methanol with Amberlyst® 15 as catalyst yielded the epimeric spiro ketals 4a and 4b along with a minor amount of the pyranoid ketal 2. Contrary to a literature report, treatment of KBBL in 2% methanolic HCl gave the rearranged methyl ester 3 rather than ketal 2. Ketals 2, 4a, and 4b are potentially useful intermediates for the further elaboration of the ascorbic acid nucleus of KBBL because the ketone and one hydroxyl of the butyrolactone nucleus (derived from ascorbic acid) are simultaneously protected as an internal ketal. X-Ray structures of these compounds were obtained, contributing to our knowledge of the structure of the KBBL family of immunostimulants.