bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nucleic‐Acid Analogues with Restricted Conformational Flexibility in the Sugar‐Phosphate Backbone (‘bicyclo‐DNA’). Part 3. Synthesis, pairing properties, and calorimetric determination of duplex and triplex stability of decanucleotides from [(3′S,5′R)‐2′‐deoxy‐3′,5′‐ ethano‐β ‐D‐ribofuranosyl]adenine and ‐thymine
Authors: Tarköy Markus , Bolli Martin , Leumann Christian 
Published: December 2004

AbstractThe synthesis of a new type of oligonucleotide (‘bicyclooligodeoxynucleotide’ = bcd(Xn)) displaying less conformational flexibility in its sugar‐phosphate backbone is described, and a characterization of the pairing properties and energetics of the decamers bcd(T10) and bcd (A10) with each other and with complementary RNA and DNA sequences by UV‐spectroscopic and calorimetric techniques is given. The results can be summarized as follows: (i) bcd(T10) pairs less strongly to complementary RNA and DNA, whereas bcd(A10) forms stronger duplexes relative to the natural system. (ii) bcd(A10) discriminates between a complementary oligodeoxynucleotide with a mismatch in the center in the same way as d(A10), indicating equal base‐pairing selectivity. (iii) bcd(A10) forms more stable triplexes with d(T10) of the pyrimidine‐purine‐pyrimidine (py · pu · py) motif than d(A10). (iv) The stability of duplexes containing a bicyclic strand is more sensitive towards salt concentration. The higher sensitivity in bcd(A10) containing duplexes is due to a higher differential cation uptake. (v) Differential scanning calorimetric (DSC) analysis of duplex‐formation enthalpies shows ΔHvH in all duplexes containing bicyclooligonucleotides to be more negative than ΔHcal, which is compatible with the formation of catenated structures. (vi) Isothermal titration calorimetry (ITC) provides a complete set of thermodynamic data including duplex and triplex association constants for the systems d(A10)/d(T10), bcd(A10)/d(T10), d(A10)/bcd(T10), bcd(A10)/bcd(T10). (vii) All duplexes containing bicyclic strands show a (numerically) reduced pairing entropy term with respect to that of the natural system. (viii) Enthalpies from DSC and ITC are similar, suggesting that the enthalpic contribution from ordered single strands to the overall duplex‐formation enthalpy plays a minor role in the duplexes investigated.
Intramolecular Dynamics of Tetranuclear Iridium Carbonyl Cluster Compounds. Part V. Polysubstituted derivatives of [Ir4(CO)12]
Authors: Strawczynski Andrés , Hall Chris , Bondietti Giacomo , Ros Renzo , Roulet Raymond 
Published: December 2004

AbstractThe dynamic behaviour of twelve polysubstituted derivatives of [Ir4(CO)12] has been investigated in solution, using 2D‐EXSY, and VT‐31P‐ and 13C‐NMR. [Ir4(CO)6(μ2‐CO)3(η4‐diarsine) PPh3] and [Ir4(CO)6(μ2‐CO)3(η4‐nor‐bornadiene)(PMePh2)] exhibit two isomeric forms in solution, which interconvert through an intramolecular change of basal face. The related cluster [Ir4(CO)6(μ2‐CO)3(η4‐norbornadiene)PPh3] exists as a single isomer in solution. It displays rotation of CO ligands about the apical Ir‐atom, followed by two consecutive changes of basal face. The tetrasubstituted clusters with two chelating ligands [Ir4(CO)5(μ2‐CO)3(η4‐diolefin)2] also exhibit rotation of apical CO's, the activation energy increases with greater steric hindrance of the radical ligands. A quantitative analysis of the 31P‐ and 13C‐2D‐EXSY spectra followed by simulation of the corresponding VT‐NMR spectra of [IR4(CO)5(μ2‐CO)3(μ2‐L)2] (L = bis(diphenylphosphino)methane and 1,3‐bis(diphenylphosphino)propane) revealed a pairwise averaging of the P‐atoms, caused by two parallel changes of basal face averaging all CO ligands. In addition, the restricted rotation of ligands about the apical Ir‐atom was identified at higher temperatures. The remaining clusters are either rigid on the NMR time scale, or display CO‐scrambling about a single Ir‐atom.
Synthesis and Evaluation as Irreversible Glycosidase Inhibitors of Mono‐ and Oligo(glycosylthio)benzoquinones
Authors: Schnabelrauch Matthias , Vasella Andrea , Withers Stephen G. 
Published: December 2004

AbstractThe mono(glucosylthio)hydroquinone 2 was prepared by S‐glycosidation of 2‐mercaptobenzene‐1,4‐diol and by addition of the acetylated 1‐thioglucose 3 to benzo‐1,4‐quinone (Scheme 1). The second, higher yielding procedure was adopted for the preparation of a range of (glucosylthio)hydroquinones. Addition of 3 to 2‐chlorobenzo‐1,4‐quinone, followed by oxidation gave the 1‐thioglucosides 7 and 12 (1.3:1), while addition of HCl to the (glucosylthio)quinone 4 and oxidation gave mainly 12 (Scheme 1). Similarly, the bis(glucosylthio)hydroquinone 33 was obtained from 3 and 4 (Scheme 4), and the (cellobiosylthio)hydroquinone 18 from the thiol 16 and benzo‐1,4‐quinone (Scheme 2). Addition of the 4‐thioglucoside 21 to benzo‐1,4‐quinone (→22) and to 4 was followed by oxidation to yield the mono(glucosylthio)quinone 23 and the disubstituted quinones 24 and 25, respectively (Scheme 3). A mixture 24/25 was also obtained from the addition of 3 to 23. The tris(glucosylthio)hydroquinone 36 was obtained by addition/elimination to the dichloroquinone 29 or the dimesylate 31, which was prepared in a simplified way (Scheme 4). The tetrakis(glucosylthio)hydroquinone 37 was obtained from 3 and chloranil, followed by reduction. The acylated hydroquinones were deprotected (→5, 9, 14, 19, 27, 34, and 38), and oxidized to the corresponding quinones (6, 10, 15, 20, 28, 35, and 40). The (glucosylthio)quinones 6, 15, 20, 28, and 35 were tested as time‐dependent inactivators of a retaining β‐1,4‐glucosidase from Agrobacterium faecalis (Abg), which has a strong exo‐glucosidase action (Table 1). Similarly, compounds 20, 28, and 35 were tested with a cellulase from Cellulomonas fimi (Cex) which degrades cellulose and cellooligosaccharides by hydrolysis of a cellobiose unit from the nonreducing terminus. The most effective inactivators for Abg were 6, 15, and 35, which inactivated this enzyme with similar second‐order rate constants. (Glycosylthio)quinone 28 was the worst inactivator and did not show normal saturation behaviour. Inactivation of Cex by the (glycosylthio)quinones was 3–500 times slower than that of Abg. The three inactivators 20, 28, and 35 had approximately the same efficacy with Cex, suggesting that they bind to this enzyme in a similar mode. Further, the Ki values observed are very similar to Km values measured for aryl cellobiosides, implying that they bind at the active site.
The Influence of the Axial Chirality of Dibenzo[a,c]cyclooctene on the Configuration of Its Photo‐Diels‐Alder Adducts
Authors: Burger Ulrich , Lottaz Pierre‐André , Millasson Patricia , Bernardinelli Gérard 
Published: December 2004

AbstractTriazole‐diones and naphthoquinone are shown to add in a photochemical [4+2] reaction to the strongly twisted title diene 1. With 1, 4‐naphthoquione, the process is also accompanied by a [2+2] cycloaddition. When the pure atropisomer (−)‐1 is irradiated in presence of 2, 3‐dichloro‐ 1, 4‐naphthoquinone (9), the axial chirality of the diene is preserved. Moreover, it is found to exert complete control over the chirality induced in the resulting spiro‐dihydropyrane 10. Absolute configuration are determined by X‐ray crystallography. In absence of a photo‐dienophile, the axially chiral, dextrorotatory 6‐phenyldibenzo[a,ccyclootene] ((++)‐11) undergoes a stereospecific electrocyclization to give levorotatory 4b,6a‐dihydro‐5‐phenylcyclobuta[l]phenanthrene ((−)‐13). Thus, only one out of two possible, disrotatory modes of ring closure is preferred.
Nucleosides. Part LVI. Aminolysis of carbamates of adenosine and cytidine
Authors: Sigmund Harald , Pfleiderer Wolfgang 
Published: December 2004

AbstractThe 2‐(4‐nitrophenyl)ethoxycarbonyl(npeoc) group, introduced 1984 as protecting group for exocyclic amino functions of nucleic‐acid bases, reacts with amines under mild conditions to urea derivatives. Treatment of 2′,5′‐di‐O‐acetyl‐N6‐[2‐(4‐nitrophenyl) ethoxycarbonyl]cordycepin (3) with NH3/MeOH overnight at room temperature affords cordycepin (4) and N6‐carbamoylcordycepin (5). Preliminary investigations towards the elucidation of the reaction mechanism indicate that the aminolysis proceeds via an addition‐elimination or an isocyanate mechanism, depending on the reaction conditions. The phenoxycarbonyl (phoc) group at N6 or N4 was chosen to study the mild conversion of carbamates with aromatic amines into ureas of adenosine and cytidine, respectively.
Preparation of Oxazolidine‐Containing Peptides: Unusual effects in RhIII‐catalyzed acetalizations of aldehydes with urethane‐protected serine and threonine esters and with dipeptides containing serine or threonine residues at the N‐terminus
Authors: Seebach Dieter , Sommerfeld Thimo L. , Jiang Qiongzhong , Venanzi Luigi M. 
Published: December 2004

AbstractThe cyclization reaction of aldehydes with Z‐ and Boc‐protected β‐hydroxyamino‐acid esters (Tables 1 and 2), or of dipeptides containing serine or threonine at the N‐terminus (Table 3), to give oxazolidine derivatives, occurs in the presence of isopropyl orthoformate and catalytic amounts of [Rh(MeCN)3(triphos)](CF3SO3)3. The reaction may be carried out under kinetic or under thermodynamic control, so that the ratio of the two possible epimeric products can be changed. The protecting group can be removed from the 3‐position of the oxazolidine ring, and the resulting NH group can be coupled with another amino acid. Thus, a new method for the preparation of peptides containing β‐hydroxy‐amino acid‐derived oxazolidines (‘pseudo‐prolines’) is available. N‐Neopentyl‐substituted tripeptides are also described.
Synthetic Attempts towards ‘Aromatic’ Nonafulvenes
Authors: Chai Shengyong , Neuenschwander Markus 
Published: December 2004

AbstractAccording to their spectroscopic behavior, four classes of nonafulvenes may be distinguished, but, so far, only three classes have been identified. Type‐A nonafulvenes (including parent 1a) are typically olefinic molecules with strongly alternating bond lengths and a nonplanar nine‐membered ring. Type‐B nonafulvenes are characterized by four pairs of equivalent ring H‐atoms and ring C‐atoms. Spectra of both Type‐A and Type‐B nonafulvenes are not dependent on temperature and solvent polarity. However, spectra of Type‐C nonafulvenes (including prototype 1d with R1 = R2 = NMe2) are strongly influenced by temperature and solvent polarity due to an equilibrium 1⇄1± between the nonpolar olefinic 1 and dipolar planarized 1±. So far, Type‐D nonafulvenes occurring exclusively in the dipolar form 1± were unknown. Synthetic attempts towards nonafulvenes of Type D are described and problems encountered in nonafulvene syntheses are discussed. Several new cyclononatetraenes and four new nonafulvenes (or nonafulvalenes) 31, 1n, 3, and 5 have been synthesized. Spectroscopic evidence shows that 11,12‐bis(diethylamino)nonatriafulvalene 5 is the first Type‐D nonafulvene.
Synthesis of Benzazepine Analogues of Noscapine
Authors: Schmidhammer Helmut , Scherb‐Bukowiecki Eva , Mayer Thomas A. , Schönholzer Peter 
Published: December 2004

AbstractThe synthesis of benzazepine analogues of the opium alkaloid noscapine (1) is described. The benzazepines 2 and 3 were prepared starting from nornarceine ethyl ester (4; readily available from 1) in several steps. X‐Ray analysis of compound 2 revealed that it is not a diastereosisomer mixture but a racemate of the threo‐form and thus has the same configuration as 1.
Synthesis of Enantiomerically Pure Ferrocenes from Glycofuranosyl‐cyclopentadienes, synthetic equivalents of (alkoxyalkyl)fulvenes
Authors: Vedø Per , Chauvin Rémi , Li Zhi , Bernet Bruno , Vasella Andrea 
Published: December 2004

AbstractCyclopentadienyl C‐glycosides (= glycosyl‐cyclopentadienes) have been prepared as latent fulvenes. Their reaction with nucleophiles leads to cyclopentadienes substituted with (protected) alditol moieties and, hence, to enantiomerically pure metallocenes. Treatment of 1 with cyclopentadienyl anion gave the epimeric glycosyl‐cyclopentadienes 6/7 (Scheme 1). Each epimer consisted of a ca. 1:1 mixture of the 1, 3‐and 1, 4‐cyclopentadienes a and b, respectively, which were separated by prep. HPLC. Slow regioisomerisation occurred at room temperature. Diels‐Alder addition of N‐phenylmaleimide to 6a/b ca. 3:7 at room temperature yielded three ‘endo’‐adducts, i.e., a disubstituted alkene (8 or 9, 25%) and the trisubstituted alkenes 10 (45%) and 11 (13%). The structure of 10 was established by X‐ray analysis. Reduction of 6/7 (after isolation or in situ) with LiAlH4 gave the cyclopentadienylmannitols 12a/b (80%) which were converted to the silyl ethers 13a/b (Scheme 2). Lithiation of 13a/b and reaction with FeCl2 or TiCl4 led to the symmetric ferrocene 14 (76%) and the titanocene 15 (34%), respectively. The mixed ferrocene 16 (63%) was prepared from 13a/b and pentamethylcyclopentadiene. Treatment of 6/7 with PhLi at −78° gave a 5:3 mixture of the 1‐C‐phenylated alcohols 17a/b and 18a/b (71%) which were silylated to 19a/b and 20a/b, respectively. Lithiation of 19/20 and reaction with FeCl2 afforded the symmetric ferrocenes 21 and 22 and the mixed ferrocene 23 (54:15:31, 79%) which were partially separated by MPLC. The configuration at C(1) of 17–22 was assigned on the basis of a conformational analysis. The reaction of the ribofuranose 24 with cyclopentadienylsodium led to the epimeric C‐glycosides 27a/b and 28a (57%, ca. 1:1, Scheme 3). The in‐situ reduction of 27/28 with LiAlH4 followed by isopropylidenation gave 25a/b (65%) which were transformed into the ferrocene 26 (79%) using the standard method. Phenylation of 27/28, desilylation, and isopropylidenation gave a 20:1 mixture of 33a/b and 34a/b (86%) which was separated by prep. HPLC. The same mixture was obtained upon phenylation of the fulvene 32 which was obtained in 36% yield from the reaction of the aldehydo‐ribose 30 with cyclopentadienylsodium at −100°. Lithiation of 33/34 and reaction with FeCl2 gave the symmetric ferrocene 35 (88%). Similarly, the aldehydo‐arabinose 36 was transformed via the fulvene 37 (32%) into a 18:1 mixture of 38a/b and 39a/b (78%) and, hence, into the ferrocene 40 (83%). Conformational analysis allowed to assign the configuration of 33–35, whereas an X‐ray analysis of 40 established the (1S)‐configuration of 38a/b and 40. The opposite configuration at C(1) of 38a/b and 33a/b was established by chemical degradation (Scheme 4). Hydrogenation (→41 and 44, resp.), deprotection (→ 42 and 45, resp.), NaIO4 oxidation, and NaBH4 reduction yielded (+)‐(S)‐43 and (−)‐(R)‐43, respectively.
Synthesis of β ‐Cyperone via Fungal Hydroxylation of thujone‐derived tricyclic cyclopropanes
Authors: Kutney James P. , Wagner Jürgen , Hewitt Gary M. 
Published: December 2004

AbstractSynthesis of optically active sesquiterpenes with a eudesmane C‐skeleton from the chiral starting material thujone involves transformation of a tricyclic intermediate (1R,2R,4S)‐1,7‐dimethyl‐4‐(1‐methylethyl)tricyclo[4.4.0.02,4]dec‐6‐en‐8‐one (2) into the bicyclic compound β ‐cyperone (5). Hydroxylation of 2 at C(5) or C(11) permits subsequent opening of the cyclopropane ring and rearrangement to β ‐cyperone. In this publication, studies involving hydroxylation of 2 by fungal cultures are presented. The resultant products are useful intermediates in efficient synthesis of eudesmane sesquiterpenes. Of five fungi tested, Rhizopus oryzae ATCC 11145 proved most versatile. It hydroxylates at the exocyclic C(11) position in high yield (70%) and, to a lesser extent, at C(5) (5%). Enzymatic activity appears at the end of growth phase and at least 2.2 g of 2 per liter can be metabolized without significant loss of product yield. A second fungus, Cunninghamella echinulata ATCC 9244, proved most useful for hydroxylation of derivatives of 2 for the preparation of derivatives of β ‐cyperone, although product yields were low (2–20%), some derivatives were nonreactive, and hydroxylation at C(9) occurred. The relationship between precursor structure and enzyme affinity is discussed.
Nucleotides. Part XLIV. Synthesis, characterization, and biological activity of monomeric and trimeric cordycepin‐cholesterol conjugates and inhibition of HIV‐1 replication
Authors: Wasner Marita , Pfleiderer Wolfgang , Henderson Earl E. , Suhadolnik Robert J. 
Published: December 2004

AbstractThe antivirally active 3′‐deoxyadenylyl‐(2′–5′)‐3′‐deoxyadenylyl‐(2′–5′)‐3′‐deoxyadenosine (cordycepin trimer core) was modified at the 2′‐ or 5′‐terminus, by attachment of cholesterol via a carbonate bond (→ 15) or a succinate linker (→ 16 and 27) to improve cell permeability. The corresponding monomeric conjugates 4, 7, and 21 of cordycepin were prepared as model substances to study the applicability of the anticipated protecting groups – the monomethoxytrityl (MeOTr), the (tert‐butyl)dimethylsilyl (tbds), and the β ‐eliminating 2‐(4‐nitrophenyl)ethyl (npe) and 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) groups – for the final deblocking steps without harming the ester bonds of the conjugate trimers. The syntheses were performed in solution using phosphoramidite chemistry. The fully protected trimer conjugates 13, 14, and 26 as well as all intermediates were characterized by elemental analyses, UV and 1H‐NMR spectra. The deblocked conjugates 15, 16, and 27 were pure according to HPLC and showed the correct compositions by mass spectra. Comparative biological studies indicated that cordycepincholesterol conjugate trimers 16 and 27 were 333‐ and 1000‐fold, respectively, more potent inhibitors of HIV‐1‐induced syncytia formation than cordycepin trimer core.
The Revised Structure of the Norditerpenoid Alkaloid Peregrine
Authors: de la Fuente Gabriel , Ruíz‐Mesía Lastenia , Rodriguez Matías L. 
Published: December 2004

AbstractThe structure of peregrine (1), a norditerpenoid alkaloid isolated from Delphinium peregrinum var. elongatum BOISS., was revised on the basis of the 1H‐COSY, HMQC, HMBC, and ROESY NMR spectra and of the X‐ray analysis of its parent alcohol 2. Some of the 13C‐NMR resonances of 1 and the related alkaloids peregrine alcohol (2), 14‐O‐acetylperegrine (3), bicoloridine (4), bicoloridine alcohol (5), 6‐O‐acetylbicolorine (6), bicolorine (7), and 14‐O‐acetylbicolorine (8), were also reassigned.
A Kinetic Analysis of the Reaction Catalysed by (Hydroxymethyl)bilane Synthase
Authors: Niemann Annette C. , Hädener Alfons , Matzinger Peter K. 
Published: December 2004

Abstract(Hydroxymethyl)bilane synthase (HMBS) catalyses the conversion of porphobilinogen (2) into the (hydroxymethyl)bilane derivative 3, a linear tetrapyrrolic intermediate in the biosynthesis of haem, chlorophyll, and related pigments. The conversion involves the sequential formation of four intermediate covalent enzyme‐substrate complexes, before the product is released. We analysed the pre‐steady‐state kinetics of the formation of the complexes, taking advantage of their remarkable chemical stability allowing chromatographic separation. The experimental approach involved the generation of the complexes while HMBS was immobilised on an anion‐exchange column. A solution being 0.2 Km in substrate was pumped through the column during a time interval which was varied to sample the pre‐steady‐state period. Then, the enzyme and enzyme‐substrate complexes were eluted and their proportions evaluated. A computer simulation of the pre‐steady‐state time course, in combination with a χ2 fitting to the experimental data, allowed the specificity constants kcat/Km for the individual steps of the process to be derived. By repeating the analysis with variants of HMBS in which specific amino acids were replaced by others, we demonstrated that it is possible to trace the consequences of amino‐acid replacements down to the individual steps of the reaction sequence. Since the positions of the amino acids concerned in the three‐dimensional structure were known, detailed structure‐function relationships become evident in this way.
Synthesis of Carbo‐ and Heterocyclic Cycloprop[f]indenes via cycloaddition of dienes to cyclopropenes
Authors: Müller Paul , Miao Zhongshan 
Published: December 2004

AbstractThe heterocyclic cycloprop[f]indene 19 was synthesized via cycloaddition of diene 10 to the cyclopropene 11a and subsequent base‐induced aromatization. While 19 is isolable, although very short‐lived, the oxa analogue 18 decomposed under the conditions required for its preparation. The difluoro derivatives 14 and 15, in which the heterocyclic moiety is saturated, are accessible by the cycloaddition approach, but the corresponding dichlorides are again not isolable. Cycloprop[f]indenes carrying substituents at C(4) have been obtained via cycloaddition of 22b to 1‐bromo‐2‐chlorocyclopropene. The key step of the sequence is a double Curtius degradation of the cycloadduct 23b to the ketone 27a. While aromatization of the alcohol 27b provided the cycloprop[f]indenol 28b, the reaction failed with 27a. Attempts to convert 28b to 1,3‐dihydrocycloprop[f]indene (25) via the methanesulfonate 28d failed.
Synthesis of [Ir3Rh(CO)12] and Fluxional Behaviour of Some of Its Substituted Derivatives
Authors: Bondietti Giacomo , Laurenczy Gábor , Ros Renzo , Roulet Raymond 
Published: December 2004

AbstractThe redox condensation of [Ir(CO)4]–, [Ir(cod)(THF)2]+, and [Rh(cod)(THF)2]+ (cod = cycloocta‐1,5‐diene) followed by saturation with CO (1 atm) in THF afforded the first synthetic route to pure [Ir3Rh(CO)12] (1). Substitution of CO by monodentate ligands gave [Ir3Rh(CO)8(μ2‐CO)3L] (L = Br–,2; I–, 3; bicyclo[2.2.1]hept‐2‐ene, 4; PPh3, 5). Clusters 2–5 have Cs symmetry with the ligand L bound to the basal Rh‐atom in axial position. They are fluxional in solution at the NMR time scale due to two CO scrambling processes: the merry‐go‐round of basal CO's and changes of basal face. An additional process takes place in 5 above room temperature: the intramolecular migration of PPh3 from the Rh‐ to a basal Ir‐atom. Substitution of CO by polydentate ligands gave [Ir3Rh(CO)7–x(μ2‐CO)3(η4‐L)x] (L = bicyclo[2.2.1]hepta‐2,5‐diene (= norbornadiene; nbd), x = 1, 6; L = nbd, x = 2, 13; L = cod, x = 1, 7; L = cod x = 2, 15), [Ir3Rh(CO)7(μ2‐CO)3(η2‐diars)] (diars = 1,2‐phenylenebis‐(dimethylarsine); 8), [Ir3Rh(CO)7(μ2‐CO)3(η4‐L)] (L = methylenebis(diphenylphosphine), bonded to 2 basal Ir‐atom (9a) or one Ir‐ and one Rh‐atom (9b)), [Ir3Rh(CO)6(μ2‐CO)3(η4‐nbd)PPh3] (12), and [Ir3Rh(CO)6(μ2‐CO)3(μ3‐L)] (L = 1,3,5‐trithiane, 10; L = CH(PPh2)3, 11). Complexes 6–8, 9a, 10, and 11 have Cs symmetry, the others C1 symmetry. They are fluxional in solution due to CO scrambling processes involving 1, 3, or 4 metal centres as deduced from 2D‐EXSY spectra. Comparison of the activation energies of these processes with those of the isostructural Ir4 and Ir2Rh2 compounds showed that substitution of Ir by Rh in the basal face of an Ir4 compound slows the processes involving 3 or 4 metal centres (merry‐go‐round and change of basal face), but increases the rate of carbonyl rotation about an Ir‐atom.
Synthesis and reactions of 2‐(alkylthio)‐4,4‐dimenthyl‐1,3‐thiazole‐5(4H)‐thiones
Authors: Shi Junxing , Linden Anthony , Heimgartner Heinz 
Published: December 2004

AbstractSix 2‐(alkylthio)‐substituted 4,4‐dimethyl‐1,3‐thiazole‐5(4H)‐thiones were synthesized according to a new method. The reactions of these compounds with allyl‐ and benzyllithium reagents, 1,3‐dipoles, and dimethyl acetylenedicarboxylate proceeded in a similar manner to 2‐alkyl‐substituted analogues, while methyllithium reacted in a different way yielding trithio‐orthoester derivatives.