Monolactones

On hydrolysis by boiling aqueous solution of barium hydroxide, isatidine (p. 603) yields two acid products. Isatinedc acid, CioHigOg, m.p. 148-5°, [a]ff° + 86° (HjO), which appears to contain one ethylenic linkage, one carboxyl group and one per-carboxyl group (R. CO. O. O), the evidence for the latter being the liberation of iodine from neutral or alkaline potassium iodide solution. The second product is isatinedc monolactonic add, CiqH 405, m.p. 197-8°, + 108-8°, which contains... 

Hoye demonstrated that the carbonyl group that lies on the C2-symmetric axis in keto diacid 119 can be reduced to alcohol 120. When followed by acid-catalyzed lactonization of the hydroxyl group with either a C-l or C-9 carboxyl group, monolactone 121 or ent-121 can be produced, thus realizing the desymmetrization of substrate 119 (Scheme 8-45). 

McIntosh CA, Mansell RL (1997) Three-dimensional analysis of Umonin, Umonoate a-ring monolactone, and naringin in the fruit of three varieties of Citrus paradisi. 1 Agric Food Chem 45 2876-2883... 

Ozonolysis of 3,5-dihydroxy-3,5-di-(w-buten-3-yl)pyrrolizidine (167c) resulted in the formation of pyrrolizidine-3,5-dihydro xy-3,5-bis(3 -propionic acid) monolactone (170). Similar treatment of 3,5-dihydro xy-3,5-bis(phenylethynyl)pyrrolizidine (167b) afforded stereoisomeric 3,5-dihydroxypyrrolizidine-3,5-dicarboxylic acids (171a and 171b). 

Maier, V. P. Beverly, G. D. Limonin monolactone, the nonbitter precursor responsible for delayed bitterness in certain citrus juices. J. Food Sci., 1968, J3, A88-A92. 

Methods for the chemical synthesis of glycuronic acids include (i) reduction of the monolactones of aldaric acids, (ii) oxidation of the primary alcoholic group of aldose derivatives, (iii) oxidative degradation procedures, (iv) chain-extension reactions on dialdoses, and (v) epimerization reactions. 

Morgan and Wolfrom isolated an a-pyrone, probably 4-acetoxy-6-(ethoxycarbonyl)-2//-2-pyrone (89), from the reaction of monoethyl DL-galactarate or its monolactone with acetic anhydride and sodium acetate at 100 °C the authors postulated the intermediate formation of an enolic lactone in this transformation.261... 

XIX). Lactones react like substituted hydroxy acids, provided that the lactone ring is sufficiently stable to resist hydrolysis during the oxidation reaction. Thus, the carbon chain of the 3,6-monolactone (XX) of n-sacchaiic acid 66 67 is cleaved between carbon atoms 4 and 5 to yield XXI, which is an ester of glyoxylic acid with n-threuronic acid... 

The most thorough examination of a species in the Picrodendraceae was conducted by Koike, Ohmoto, and coworkers on P. baccatum (36,46,53-56,77,78). This tree is endemic to the West Indies. The plants investigated by the authors were harvested in the Botanical Garden of Bogor, Indonesia in 1986. In the next 15-20 years this Japanese group isolated 9 monolactone sesquiterpenes and 19 norditerpene picrotoxanes from this plant material. At first, these researchers examined a relatively small sample of the bark of the tree to determine the structural type of the toxins. Thus, 1.2 kg of dried bark were extracted successively with n-hexane. 

So far, Dendrobium species have yielded 21 pseudoalkaloids of the picrotoxane type and 27 sesquiterpene picrotoxanes (5 dilactones, 20 monolactones. 

Hydrolysis with aqueous mercuric chloride in the presence of cadmium carbonate removed the thioethoxy groups in ethyl tetraacetyl-thiostreptobiosaminide diethyl mercaptal. Crystalline tetraacetylstrep-tobiosamine was obtained in this manner. Bromine oxidation of tetraacetylstreptobiosamine in the presence of strontium carbonate yielded an acid which, after reacetylation, was obtained as the crystalline pentaacetyl derivative. The analytical data and the results of potentio-metric titrations for this oxidation product, designated pentaacetyl-streptobiosamic acid monolactone, were in agreement with the formula, Ci3Hi6NOio(CH3CO)5, required for a dibasic acid monolactone. A crystalline monomethyl ester of the substance was prepared. The established formula shows that all hydroxyl groups present are acetylated or lactonized. 

Hydrolysis of pentaacetylstreptobiosamic acid monolactone in refluxing 2.5 N hydrochloric acid yielded a crystalline compound derived from the streptose moiety. This compound was designated streptosonic acid monolactone and was further characterized as its diacetate. The hydrolyzate was shown to contain N-methyl-L-glucosamine. 

Analysis of streptosonic acid monolactone showed a composition corresponding to the formula CsHgOe. The formulation of this compound as a monolj,ctone of a dibasic acid was based on its behavior during potentiometric titration, when neutral equivalents of 175 and 87.5 were... 

Confirmatory evidence for streptosonic acid diamide existing as structure XXI was obtained by a study of the oxidation products of streptosonic acid monolactone (XXIII). When this compound was oxidized with two moles of periodic acid, two of the cleavage products were identified as glyoxylic acid (XXIV) and oxalic acid (XXV). The suggested course of the oxidation, on the basis of structure XXIII, is shown... 

Assuming structure XXIII for streptosonic acid monolactone and structure XX for didesoxydihydrostreptobiosamine, streptobiosamic acid monolactone would be XXVI. 

Unlike the other streptobiosamine derivatives (Table IV, page 383) streptobiosamic acid monolactone formed a pentaacetyl derivative " rather than a tetraacetyl compound. Also, acetylation of streptosonic acid monolactone yielded a diacetyl derivative. It was pointed out that either the ordinarily resistant tertiary hydroxyl group had been acetylated in these compounds (XXVII) or that the lactone ring had shifted from the 7- to the /3-position, during the acetylation, with the introduction of an acetyl group at carbon atom four (XXVIII). Whatever the positions of the ester groupings in pentaacetylstreptobiosamic... 

---