Biogenetic-type synthesis of (.+-.)-phyllodulcin, a sweet principle of Hydrangea serrata Seringe var. thunbergii Sugimoto (Studies on the .BETA.-carbonyl compounds connected with the .BETA.-polyketides. VI).

1,3,2‐(2H)‐dioxaborine polymethine dyes on the base of dehydroacetic acid — effective fluorescent amine probes

“…Therefore, in the case of boron difluoride complexes of chalcones of dehydroacetic acid, which per se are dyes 3a, 5a, and 6a (the dyes 5a and 6a react with amines similar to dye 3a), the similar mechanism for the opening the pyran cycle possibly realizes, that was previously observed for free chalcones of the type C [8][9][10]. Due to the higher electron accepting properties of annelated 2,2-difluoro-1,3,2-(2H)-dioxaborine fragment in comparison with free -diketonate group, the carboxylic acid formed by opening of the pyran cycle is stronger, than formed from C. That's why probable formation of more stable salt is more evident.…”

“…In 1885 Heitinger first obtained 2,6-dimethylpyridine-4-one B (R = H) via reaction of dehydroacetic acid A with ammonia [1]. A large amount of works related to the reactions of dehydroacetic acid [2][3][4][5][6][7] and its derivatives of type C [8][9][10] with the amines have been published since then. The latter form open-chain decarboxylated products by the reaction with amines.…”

“…The latter form open-chain decarboxylated products by the reaction with amines. Depending on the nature of substituents, amines and the reaction conditions the monosubstituted enamine derivatives of 1,3,5-triketones of type D [8,9] or disubstituted derivatives of type E could be obtained [10]. In all cases amine attacks the C-6 position of the pyranone system which leads to its further opening and decarboxylation of the obtained acid (Scheme 1).…”

Synthesis of Heterocyclic Compounds from the Reactions of Dehydroacetic Acid (DHA) and Its Derivatives

“…The reaction between the DHA with N,N-dimethylformamide dimethylacetal gives 4-hydroxy-6-methyl-2-oxo-3-[3-dimethylaminoacryloyl]-2H-pyran(66). Thus, reactions of DHA with N-amino-1,2,4-triazole(68), hydrazine and N-aminopyridinium salts (71) produce N,N ′ -linked bi(heteroaryls) compounds (69, 70, 72), respectively [64][65][66]. NH 2 OH.HCl Many interesting versions are encountered in the reaction of hydrazine with N-amino heterocycles.…”

“…Thus, reactions of DHA with N-amino-1,2,4-triazole(68), hydrazine and N-aminopyridinium salts (71) produce N,N ′ -linked bi(heteroaryls) compounds (69, 70, 72), respectively [64][65][66]. The alcohols used in this transformation include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol and sterically hindered t-butyl alcohol.SECTION III: MISCELLANEOUS REACTIONSA)Biogenetic synthesis of phenylisocoumarin A biogenetic-type synthesis of a dihydroisocoumarin, 3,4-dihydro-8-hydroxy-3-phenylisocoumarin (85) from DHA and trans-cinnamaldehyde (77) modeled on the polyketide mode of biosynthesis has been reported by Takeuchi et al68,69 This is a multistep synthesis and reaction sequence is outlined in Scheme1.A new series of macrocyclic ligands with different ring sizes (14-, 15-and 16-membered) are synthesized from DHA in a two-step reaction process involving Williamson's condensation (86) andSchiff base cyclization (87) reactions with various diamines such as 1,2-or 1,3-diaminoalkane, carbohydrazide and thiocarbohydrazide 70. Both these reactions probably proceed through the condensation of initial formed heptane-2,4,6-trione with thiourea and guanidine.BenzodiazepinesThe reaction of o-phenylenediamine (OPD) with DHA in different alcohols leads to the formation of 2alkoxycarbonylmethylenebenzodiazepines (75) and 4-acetylmethylenebenzodiazepinones (76) 49.…”