A group additivity approach for the estimation of heat capacities of organic liquids and solids at 298 K

A group additivity method is described which provides heat capacity estimates of the condensed phase. The data base consists of 810 liquids and 446 solids. Group values for carbon in various common substitution and hybridization states and for 47 functional groups are provided. The standard error of estimation using this approach on this data base is 19.5 (liquids) and 26.9 J/ (mole K) (solids). This can be compared to typical experimental uncertainties of 8.12 and 23,4 J/ (mole K) associated with these measurements, respectively. Experimental uncertainties were estimated from the numerical differences obtained for a given substance from multiple independent literature reports.     

Reaction of 5,6,7,8-Tetrahydropterin with Iron(III) Acetylacetonate. Detection of Radical Cations by Electrospray Ionization Mass Spectrometry

The experimental conditions developed for the detection of rather stable radical cations in solution by electrospray-ionization mass spectrometry (ESI-MS) of a Fe^II complex of 2-amino-5,6,7,8-tetrahydro-5-methylpteridin-4 (3H)-one ( 1c ) are used to observe the formation of the more unstable radical cations formed from 2-amino-5,6,7,8-tetrahydropteridin-4(3H)-one ( 1a ) and tris(pentane-2,4-dionato)iron(III) ([Fe^III(acac)₃]; 4 ) and to monitor their oxidation to the corresponding p-quinonoid dihydropterin complexes. These results contribute to the understanding of the important role played by 6β-5,6,7,8-tetrahydro-L -biopterin ( 1b ; a homologue of 1a ) together with iron as constituent of some cofactors. The complexes obtained from 1a and iron may be considered, e.g. as a model of the cofactor of the phenylalanine hydroxylase. Moreover, we describe an improved synthesis of 1c .     

Cyclopentenone Annulation of 2-Oxocycloalkane-1-carbonitriles

Phase-transfer alkylation of the 2-oxocycloalkane-l-carbonitriles 1a and 1b with ethyl 4-bromo-3-methoxy-2-butenoate ( 2 ), followed by deprotection and base-catalyzed cyclization gave the annulated cyclopentenones 5a and 5b , respectively, in high overall yields (Scheme 1). Stereoselective catalytic hydrogenation of 5b followed by de-ethoxycarbonylation afforded 14-oxo-cis-bicyclo[10.3.0]pentadecane-l-carbonitrile ( 7 ). Treatment of 7 with LiN(i-Pr)₂ in THF gave the known synthetic muscone precursor 8 (Scheme 2). The tricyclo[10.4.0.0^1,15]hexadecan-14-one ( 14 ) was prepared from 7 in 5 steps by a reaction sequence proceeding without affecting the chiral centres (Scheme 2). The structure of 14 was established by X-ray structure analysis (Figure).     

Ringerweiterung unter Lactonisierung von methylierten 1-(3′-Hydroxypropyl)-2-oxocyclododecan-1-carbonitrilen

Ring Enlargement by Lactonization of Methylated 1-(3′-Hydroxypropy1)-2-oxocyclododecane-1-carbonitriles The title compounds were prepared by Michael reaction of 2-oxocyclododecane-1-carbonitrile ( 1 ) and acrylaldehyde and its derivatives followed by NaBH₄ reduction or methylation of the aldehyde group with [(CH₃)₂Ti(i-PrO)₂] (Scheme 1). In all cases, the ring enlargement was performed with Bu₄NF/THF to give different methylated derivatives of 12-cyano-15-pentadecanolide ( 13 ) in 95–99% yield. The Yields of the rearrangement products are not dependent on the positions and numbers of the CH₃ groups in the side chain of 3 . The lactonization reaction is of unremarkable stereoselectivity.     

N4-Benzoylspermidine from Oncinotis tenuiloba: Analytical differentiation of the three isomeric N-benzoylspermidines

During the examination of extracts from Oncinotis tenuiloba STAPF a new polyamine, N⁴-benzoylsperimidine ( 8 ), was isolated. For unambiguous structure elucidation, it was transformed into the diacetyl derivative 13 , and the three possible N-benzoyl-substituted isomers of spermidine 5, 8 , and 11 together with their peracetylated derivatives 12–14 , respectively, were synthesized and identified.     

Die Oxidation von 3-(1-Nitro-2-oxocycloalkyl)propanal

The Oxidation of 3-(1-Nitro-2-oxocycloalkyl)propanal Oxidation of the title compound 1 with KMnO₄ under neutral conditions led to the corresponding acid 2 , 5-(2,3,4,5-tetrahydro-2-nitro-5-oxo-2-furyl)pentanoic acid ( 4 ), and 4-oxononadioic acid ( 6 ). On the basis of experimental results the mechanism of the formation of 4 is discussed (Scheme 1). Oxidation of 1 with KMnO₄ under basic conditions gave 6 which was transformed to (E)-4,5-dihydro-5(2′-oxocyclopentyliden)furan-2(3H)-one ( 12 ) with benzene/TsOH (Scheme 3). In contrast to this result the corresponding 4-oxoheptandioic acid ( 22 ) yields 1,6-dioxaspiro[4,4]nonan-2,7-dione ( 23 ) only (Scheme 4).     

Synthese des Pyrrolizidin-Alkaloides (±)-Trachelanthamidin

Synthesis of the Pyrrolizidine Alkaloid (±)-Trachelanthamidine The important intermediate in the synthesis of the title compound 8 is the diastereoisomer mixture of ethyl 2-[2-(1,3 dioxolan-2-yl)ethyl]-5-oxopyrrolidine-3-carboxylate ( 3a/3b ) which was prepared from nitromethane, acrylaldehyde, and diethyl fumarate (Scheme). Its reduction (NaBH₄, t-BuOH, MeOH) gave exclusively the trans-alcohol 4a , which was converted to the protected pyrrolidine derivative 6 . The deprotection and reduction of 6 gave the pyrrolizidine alkaloid 8 , characterized as its hydrochloride.     

The Macrocyclic Spermidine Alkaloid (−)‐(S)‐Neoperiphylline: Revision of the Structure Based on the Total Synthesis

The total synthesis of the two isomeric macrocyclic enamides 2 and 17 is described. The precursor 14 was synthesized by means of template‐assisted macrocyclization (Scheme 2). Isomerization of 14 in the presence of [Fe(CO)₅] gave 2 and 17 (Scheme 4). Structure 2 was previously assigned to the alkaloid neoperiphylline. However, the synthetic 2 showed completely different properties compared to the earlier described data of the natural compound. Surprisingly, analytical data of the second synthetic product 17 were very close to those of the natural neoperiphylline. We conclude that the previously assigned structure of neoperiphylline is erroneous and should be corrected to that of (?)‐(4S,12Z)‐4‐phenyl‐9‐[(2E)‐3‐phenylprop‐2‐enoyl]‐1,5,9‐triazacyclotridec‐12‐en‐2‐one ( 17 ).     

Amidine als Zwischenprodukte bei Umamidierungsreaktionen. 9. Mitteilung über Umamidierungsreaktionen

Amidines as Intermediates in Transamidation Reactions By loss of water in the presence of p-toluenesulfonic acid/xylole N-aminoalkyllactames form bicyclic amidines. The corresponding N-alkylaminoalkyl-lactames' react to bicyclic amidinium salts or to transamidated products, ring-enlarged by the N-alkylamino residue, respectively (s. Scheme 1). The bicyclic amidines and amidinium salts are partially hydrolyzed by KOH/H₂O to lactames (s. Scheme 2). Which of the two possible isomeric lactames are formed is discussed.     

Synthese von selektiv N- funktionalisierten Polyamin-Derivaten

Synthesis of Selectively N-Functionalized Polyamine Derivatives A threefold differently protected derivative 8 of the triamine spermidine ( 2 ) has been prepared in three steps starting from propane-1,3-diamine ( 1 ). The protected spermidine derivative 8 was converted to its spermine analogue 12 , a useful polyamine intermediate. In a convergent way, the fourfold differently protected derivative 18 of the tetraamine spermine ( 3 ) has been obtained by coupling the two different and separately prepared propane-1,3-diamine units 15 and 17 . Spermidine derivative 19 and spermine derivative 20 , both selectively protected at both primary amino groups, have been Prepared from the free polyamines 2 and 3 , respectively, in a direct approach.