Monohydrate configuration

Pyrethrolone and cinerolone make up the keto alcohol moiety of the pyrethrins. Both of these keto alcohols have one asymmetric carbon at the 4-position and a double bond in the side chain which is capable of cis-trans isomerism in the 2-position. It is possible, therefore, to have four stereoisomers for each keto alcohol. Katsuda et al. (22) show that only the ( + ) form occurs in the natural esters. Elliott (8) has shown recently, by a new procedure developed to obtain pure ( + ) pyrethrolone, that the hitherto unidentified prye-throlone C is in reality pyrethrolone contaminated with thermally isomerized material. (+) Pyrethrolone forms a crystalline monohydrate from which the pure alcohol is obtained. The natural configurations of the keto alcohols in the esters are insecticidally more active, as is the case with the acid moiety. 

Carbohydrate Components of Antibiotics. Part III. Synthesis of 3.6-Dideoxy-3-dimethylamino- 3-D-glucose Hydrochloride Monohydrate the Absolute Configuration of Mycaminose, A. B. Foster, T. D. Inch, J. Lehmann, M. Stacey, and J. M. Webber, /. Chem. Soc., (1962) 2116-2118. 

Kowalik, J. Sawka-Dobrowolska, W., and Glowiak, T., Synthesis, molecular structure, and absolute configuration of an optically active (l-amino-2-phe-nylethyl)phosphonic acid monohydrate, J. Chem. Soc., Chem. Commun., 446, 1984. 

The absolute configuration of a-D-glucopyranose monohydrate has also been confirmed directly by the anomalous scattering of the oxygen atoms.70 After the atomic positions had been refined, the structure factors were calculated by using the oxygen anomalous scatter-... 

Flaromy TP, Raleigh J, Sundaralingam M (1980) Enzyme-bound conformations of nucleotide substrates. X-ray structure and absolute configuration of 8,5 -cycloadenosine monohydrate. Biochemistry 19 1718-1722... 

Optical resolutions of two a-alkoxycarboxylic acids (3a and 3b, Scheme 3) were accomplished with the neutral calcium salt of DBTA (DBTACa) in aqueous ethanol solution. [24] Preparation of the diastereoisomers is quite simple a stoichiometric mixture of DBTA monohydrate and calcium oxide had to solve in hot aqueous ethanol to form DBTACa salt and then racemic acid (3a or 3b) had to add into it. On cooling [Ca(H20)(f -3a)]DBTA.H20 or [Ca(H20)(S-3b)]DBTA.H20 cystallised. Free (S)-3a or (R)-3b was obtained from the corresponding filtrate. In the schemes and the formulas (6) or (R) stands for showing the configuration of the of the major enantiomer in the product. For example, (.S )-3a means that the isolated material contained the 6-isomer in excess, ee values are given in the Tables. 

Sceletium Alkaloids.—(-)-Mesembrane has been isolated from S. namaquense L. Bolus X-ray diffraction analysis of its hydrochloride monohydrate revealed its relative and absolute configuration (10). (-)-Mesembrine has the absolute configuration (11), in accord with (10), and it is now firmly established that alkaloids of this family belong to a single antipodal series.13... 

The centrosymmetrical UU12 configuration (Fig. 16.2) occurs frequently as in thymine [THYMIN] thymine monohydrate [THYMMH] Dihydrouracil [DHU-RAC10] dihydrothymidine [DHTHYD10] 6-methyluracil-5-acetic acid [MUR-CAC] 5,6-dihydro-2-thiouracil [DHTURC] 6-methyl-5,6-dihydrouracil [MDH-URC10] 2,4-dithiouracil [DTURAC]. 

The configuration CC22 is observed in cytosine [CYTSIN01] cytosine monohydrate [CYTOSM11] thiocytosine [THCYTOIO] 5-bromocytosine-hemi-di-oxane solvate [BRCYTS]. 

The same two-bond association is found together with the GG42 configuration in guanine hydrochloride monohydrate and in guanine hydrobromide monohydrate [GUANBM], which are also protonated at N(7). 

Cyclic Trimer Configuration. The a-cytidine [ACYTID] crystal structure contains two cyclic trimer configurations (Fig. 17.32). In one, N(H)H is engaged in a three-center bond, the other is a homodromic cycle stabilized by a- and w-cooperativity. A comparable situation is found in the crystal structure of a-pseudouridine monohydrate [APSURD] (Fig. 17.13). The glycosyl link is to uracil C(6) instead of N(l), and therefore the N(1)H group is free to donate a hydrogen bond in a homodromic cycle. 

Cyclic Pentamers. In uridine-3 -phosphate monohydrate [URIDMP10], the cyclic pentamer configuration involves )NH OH, OH- -OC CH 0(H)P, P-OH- OwH and OwH- -0=C hydrogen bonds, all of which are short (Fig. 17.11 a). It is a homodromic cycle if we include the polarizability of the ribose-0(4 )-CH-component, and probably stabilized by the strong donor/acceptor p-OH of the neutral phosphate group. 

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