Carlic acid

In this connection there should also be mentioned the formation of carlic acid (XC) from LXXXIX (formed from D-glucose as a metabolic product of the mold Penicillium charlesii G. Smith47). 

The system is very sensitive to traces of acid or to light. The l3C-NMR spectra show the equilibrium to be solvent dependent. Terrestric acid and carlic acid behave similarly.1 0 Evidently, the butenolide ring system is entirely compatible with an exo double bond at its 2-position, and accordingly the condensation of tetronic acid itself with aromatic aldehydes readily affords 3-arylidenefurandiones (73) as mixtures of two geometric isomers.155 The similar condensation with 4-hydroxycoumarin is better known but... 

Revision of the structure of naturally occurring acyltetronic acids dehy-drocarolic acid, terrestric acid and carlic acid, J.P. Jacobsen, T. Reffstrup,... 

The biosynthesis of the fungal tetronic acid carolic acid (76 a) in Penicillium charlesii is markedly different from that of patulin, multicolic acid and penicillic acid. Carbon-14 work has demonstrated that the carbon sub-unit C-3, C-4, C-9 in the acid is derived from a C-4-dicarboxylic acid such as succinate, whereas the remaining six carbons (C-1, C-2, C-5, C-6, C-7, C-8) are derived from two malonate units (C-5, C-6, C-7, C-8) and just one acetate unit (C-1, C-2) (Scheme 19) (775). It is proposed then that the biosynthesis of carolic acid proceeds from a C4-dicarboxylic acid first to either y-carboxymethyltetronic acid (196) or to carlosic acid (77 b) hydroxylation of carlosic acid then gives rise to carlic acid (77 a) which on decarboxylation produces carolic acid 176). 

Carlic, Carlosic, Carolic, Carolinic, and Viridicatic Acids... 

Scheme 1.19 Structures of carolic, carolinic, carlic, carlosic and viridicatic acids.

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