Tetrol esters

Aminopyrazole (104) with MP and MPP gave121 the 5-oxo-4,5-dihydropyrazolo[l,5-a]pyrimidines (105 and 106), whereas with DMAD the 7-oxo-4,7-dihydro derivative (108) was formed. Both types of adduct, 107 and 109, were obtained from tetrolic ester. In acetic acid, MP and and the aminopyrazole gave 4-oxo-4,7-dihydro-l//-pyrazolo[3,4-61-pyridine (110), a compound which was also formed from 104 and /J-ethoxyacrylic ester. The aminopyrazolone 111 gave the isomeric adducts 112 and 113 with DMAD together with a 1 1 molar addition product of DMAD and 112 or 113. 

Similarly, compounds 114 with EP, EPP, or tetrolic ester at 100° gave the adducts 115 in 40-45% yield.122... 

Addition of propiolicand tetrolic esters to the 2-aminobenzothiazoles 64 gave adducts 68.484,550 Some of these compounds are said to be... 

Auf der Suche nach weiteren Acetylen-Verbindungen aus den Kultur-fliissigkeiten von Pilzkulturcn sind drei neue Verbindungen isoliert wor-dcn. Das Diatretin 3 erwies sich als Hydroxysaure der Struktur CXCIX (7). Der Ester CC und das sehr polare Tetrol CCI sind weitere neue Ver-treter (54). 

Ethyl tetrolate Tetrolic acid, ethyl ester (8) 2-Butynoic acid, ethyl ester (9) (4341-76-8)... 

Russian workers102 first added pyrrolidine to propiolic, tetrolic, and phenylpropiolic esters. Later,103-105 such Michael additions were carried out in various solvents. With MP, pyrrolidine gave the trans adduct 65, whereas DMAD gave a mixture of maleate (66) and fumarate (67) esters. Akerblom106,107 has described similar additions of pyrrolidine to the furyl (68) and phenylpropiolic esters. 

Huisgen and co-workers486,490 have described a useful synthesis of N-substituted pyrroles (41) from mesoionic oxazolones (39) via the intermediates 40, which were not isolated. A variety of acetylenic esters (phenylpropiolic, propiolic, tetrolic, and DMAD) were used. The kinetics of these reactions have been studied.491 The addition of carbon... 

Factors influencing orientation in the condensation of 57 with dipolarophiles were examined by employing ethyl tetrolate in place of the phenylpropiolate. A clean reaction was not obtained, but eventually 60 was isolated indicating that the sterically less demanding ester still adds in the same manner. 

The Michael-type addition of morpholine to propiolic, tetrolic, phenylpropiolic, and acetylenedicarboxylic esters has been described by Postovskii et al.500... 

The addition of DMAD to 2-aminothiazole (25) gave 26, whereas propiolic ester gave 27, 28 and 29, all derived by Michael-type additions.549 Dunwell and Evans550,551 have also added acetylenic esters to 2-amino- (and 2-amino-4-methyl)thiazole and obtained 26 and 27 from DMAD and EP, and similar compounds from tetrolic and phenyl-propiolic esters. By independent synthesis, these compounds were shown not to have the isomeric structures derived by initial addition to the exocyclic nitrogen. 

Condensation of propiolic esters with alkenes.2 Methyl propiolate or tetrolate, when activated by complcxation with the C5H5Fe(CO)2 cation (Fp+), condense with alkenes to form cyclobutenes, 1,3-dienes, and lactones. The type of products formed depend on the structure of the alkene. 1,2-Disubstituted alkenes yield cyclobutenes and 1,3-dienes mainly, whereas 1,1-disubstiluted or trisubstituted alkenes form mainly lactones. 

Chiral diols have also been prepared starting from meso-compounds [68-71]. Since meso-compounds are, in essence, symmetric molecules, the same applies as for the other symmetric starting materials. Indeed, this is exactly what was found Even though the stereocenters of the protected heptane tetrol are far away from the ester groups that are to be hydrolysed stereoselectively, this is what happens [69, 70]. The high selectivity is partly due to the fact that the secondary alcohol groups are protected as a cyclic acetal, giving additional structural information to the enzyme (Scheme 6.20 A). A cyclic acetal also provides additional structural information in the enantioselective hydrolysis of a pentane tetrol derivative (Scheme 6.20 B) [71]. In both cases Pseudomonas fluorescens lipase (PFL) proved to be the enzyme of choice. 

Tetrolic acid has been prepared by treatment of acetoacetic ester with phosphorus pentachloride followed by dehydrochlorination of the reaction products by the base-catalyzed isomerization of 3-butynoic acid and by the treatment of 4,4-dibromo-3-methyl-2-pyrazolin-5-one with alkali followed by acidification. ... 

The first examples of a [2 -i- 2] cycloaddition at an unsaturated substituent on a carbene ligand have been recently reported." In the example shown in Scheme 2 it can be seen that the cycloadditions can occur very rapidly between enol ethers and alkynic carbene complexes. Alkynic carbene complexes can serve as surrogates for alkynic esters since the cycloadducts can be very efficiently oxidized to their corresponding esters. While the [2 + 2] cycloaddition of methyl tetrolate and dihydropyran is unknown, a comparison can be made between the alkynic carbene complex (12b), which reacts at room temperature, and the doubly activated alkynic ester (15), which will only react at 180 C with the same substrate. 

Cholic acid has been converted into 5/S-cholestane-3a,7a,12a,25-tetrol and the 3a,7a,12a,24,25-pentols. Extension of the side-chain involved conversion of the acid via the diazo-ketone (361) into a homocholanic ester derivative (362). Grignard reaction then gave the 25-hydroxy-cholestane (363). Dehydration followed by hydroxylation (OSO4) afforded the 24,25-diols with a little of the 25,26-diol. ... 

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