bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of Voltammetry to Monitor O2 Using Au/Hg Electrodes and to Control Physical Sensors on an Unattended Observatory in the Delaware Bay
Authors: Moore Tommy S. , Nuzzio Donald B. , Deering Timothy W. , Taillefert Martial , Luther George W. 
Published: July 2007

AbstractA voltammetric analyzer was used to control an observatory mooring in the Delaware Bay at the same time oxygen data were collected with solid‐state gold‐amalgam (Au/Hg) electrodes. Oxygen, temperature and salinity data were collected for 8 days and sent wirelessly back to the shore‐based laboratory. Observed oxygen saturations ranged from 70 to 171%, with a mean of 107%. The highest oxygen concentrations were observed when there were low tides during the solar maximum, indicating higher rates of production within the Delaware Bay than in coastal Atlantic Ocean waters which passed the mooring at high tides, as expected based on previous shipboard studies. Lower percent saturations indicated respiration, the decomposition of organic matter by oxygen, as the dominant process and corresponded to night periods. Upon recovery the electrodes were free of bio‐fouling. This study demonstrates that voltammetric techniques and equipment can be used in observatory and mooring systems.
Single Polypyrrole Nanowire Ammonia Gas Sensor
Authors: Hernandez Sandra C. , Chaudhuri Debangshu , Chen Wilfred , Myung Nosang V. , Mulchandani Ashok 
Published: July 2007

AbstractWe report the synthesis, electrical characterization and ammonia gas sensing with single nanowire of conducting polypyrrole. Three hundred nanometer in diameter and 50 to 60 μm long polypyrrole nanowires were synthesized by chemical polymerization inside SiO2 coated alumina membranes. Temperature dependent electrical resistance studies established that the chemically synthesized nanowires were more ordered compared to electrochemically synthesized nanowires. We further demonstrated that gas sensors based on single polypyrrole nanowire exhibited good sensitivity towards ammonia, and provided a reliable detection at concentration as low as approximately 40 ppm.
The conformational equilibrium of [2.2]paracyclophanes in solution
Authors: Ernst Ludger 
Published: July 2007

AbstractA conformational equilibrium exists in solution between two skew forms (s+ and s−) of [2.2]paracyclophane (1a). The vicinal coupling constants in the 1H‐NMR spectra of the bridge protons in the six ar‐monosubstituted derivatives 1b–1g (RCN, NO, Br, CH3, CHO, and NO2) indicate an increasing shift of the equilibrium towards one side in the order mentioned. The s+ form (positive CCCC torsional angles of the bridges) is favored in the (S) enantiomer. MM2(91) and MM3(89) molecular mechanics computations suggest that this is largely caused by increasing unfavorable nonbonded interactions in the s− conformer between the substituent and the syn proton on the ortho bridge carbon atom. Thus the „effective size”︁ of the substituent increases from 1b towards 1g.
Non‐chelate‐controlled addition of 1‐Bromo‐1‐lithio‐1‐alkenes to O‐protected lactaldehydes and 3‐alkoxybutyraldehydes
Authors: Braun Manfred , Mahler Hellmut 
Published: July 2007

AbstractNon‐chelate control is found to be the favored stereochemical outcome in the addition of the 1‐bromo‐1‐lithio‐1‐alkenes 2b and (S)‐5b to O‐protected lactaldehydes (S)‐1. Thus diastereoselectivities of 84 to 96% d.e. are reached in the formation of alcohols 3 and 6, which are converted into the O‐protected 2,3‐dihydroxyaldehyde 31 or O‐protected 1,2,3‐triols 24 and 27. In an analogous way, a non‐chelate‐controlled addition of (R)‐5b to (R)‐3‐(benzyloxy)butyraldehyde (14a) leads to the predominant formation of the diastereomer 15a (92% d.e. after enrichment by chromatography) which yields the alcohol 42a upon debromination, O‐protection, and ozonolysis. Thus, the carbenoids 2b and 5b enable the introduction of the synthons −CH2OH and −CHO into enantiomerically pure aldehydes (S)‐1 and (R)‐14 in a highly stereoselective manner. Relatively low diastereoselectivities are reached in the „mismatched”︁ combination of (R)‐5b with (S)‐1 as well as (S)‐5b with (R)‐14. The dilithium compound 20b, generated at −78°C, reacts in a retro‐1,4‐Brook rearrangement at −20°C to give vinylsilane 44b after protonation.
Bausteine von Oligosacchariden, CIX. Synthese von modifizierten Oligosacchariden der N‐Glycoproteine zur Untersuchung der Substratspezifität der N‐Acetylglucosaminyltransferase I
Authors: Paulsen Hans , Springer Matthias , Reck Folkert , Meinjohanns Ernst , Brockhausen Inka , Schachter Harry 
Published: July 2007

Building Units of Oligosaccharides, CIX. — Synthesis of Modified Oligosaccharides of N‐Glycoproteins for Substrate Specificity Studies of N‐Acetylglucosaminyltransferase IA series of modified derivatives of the trisaccharide octyl α‐D‐Man(1→3)‐[α‐D‐Man(1→6)]‐β‐D‐Man were synthesized for substrate specificity studies of N‐acetylglucosaminyltransferase I (GlcNAc‐T I). The hydroxyl groups at C‐3, C‐4 and C‐6 of the α(1→3)‐linked Mannose were replaced by hydrogen and methoxy groups. At the α(1→6)‐linked mannose the hydroxyl group at C‐2 was deoxygenated and the hydroxyl groups at C‐3, C‐4 and C‐6 were replaced by methoxy groups. The syntheses of the ten trisaccharides were carried out by the interchangeable combination of modified building blocks. The trichloroacetimidate method was favourable for all glycosylation steps.
Terpenes and terpene derivatives, XXXIV. Synthesis of rac‐porosadienone
Authors: Weyerstahl Peter , Schwope Ina 
Published: July 2007

Abstract(±)‐Porosadienone (9) is easily synthesized by starting from (±)‐2,6‐dimethylcyclohexanone via indenone 1 and dienone 4. All compounds (rac‐4‐6 and rac‐9) with the α,β,γ,δ‐dienone system are very prone to air oxidation forming the corresponding mono epoxides rac‐7, rac‐8, rac‐10, and rac‐11.
Eine unerwartete Reaktion zwischen Oxalylchlorid und atropisomeren Diaminen
Authors: Lindauer Dirk , Atzrodt Jens , Beckert Rainer , Görls Helmar 
Published: July 2007

An Unexpected Reaction between Oxalyl Chloride and Atropisomeric DiaminesChiral diamines like (S)‐1,1′‐binaphthalene‐2,2′‐diamine (3a) were acylated by oxalyl chloride to yield mainly a macrocyclic lactame 5, whereas the eight‐membered oxamide 4 was formed only in small quantity.
Progress towards a generalized solvent polarity scale: The solvatochromism of 2‐(dimethylamino)‐7‐nitrofluorene and its homomorph 2‐fluoro‐7‐nitrofluorene
Authors: Catalán Javier , López Vicenta , Pérez Pilar , Martin‐Villamil Rosa , Rodríguez José‐Gonzalo 
Published: July 2007

AbstractMore than 100 solvents and the gas phase were used to develop a solvent dipolarity‐polarizability scale that combines the medium dipolarity and polarizability into a single parameter (SPP) calculated from the UV‐visible spectra of 2‐(dimethyl‐amino)‐7‐nitrofluorene (DMANF) and its homomorph 2‐fluoro‐7‐nitrofuorene (FNF). The proposed scale compares favourably for nonprotic solvents with existing solvent polarity scales including Kosower's Z, Dimroth and Reichardt's ET(30), Brooker's χR, Dong and Winnick's Py; Kamlet, Abboud, and Taft's π*, and Drago's S′ scale. When data are derived from electronic transitions, they provide an accurate description for the solvent effect in UV‐Vis, IR, NMR, and fluorescence spectroscopy as well as in other chemical areas including thermodynamics and kinetics.
η6‐(1‐oxobenzocyclobutene)tricarbonylchromium(0): Preparation, reduction, and ring‐opening/cycloaddition chemistry of the 1‐hydroxybenzocyclobutene complex
Authors: Brands Michael , Wey Hans G. , Krömer Rainer , Krüger Carl , Butenschön Holger 
Published: July 2007

AbstractThe syntheses of the tricarbonylchromium complexes 2 and 3 of 1‐oxobenzocyclobutene and 1‐hydroxybenzocyclobutene are described. Alcoholate 6 of 3 undergoes a ring opening to the corresponding ortho‐quinodimethane intermediate between −30 and −20°C, which is trapped by dienophiles with high diastereoselectivity. While with most dienophiles products with a 1,2‐cis configuration (7, 8, 10) are formed, vinyl sulfones react in an exo‐selective cycloaddition with formation of 1,2‐trans‐configurated cycloadducts (12, 13). The configuration of the cycloadduct with phenyl vinyl sulfone is confirmed by an X‐ray crystal structure analysis. As one of the important aspects of the chemistry of benzocyclobutene complexes is the chirality of compounds like 2 and 3, the enantiomeric resolution has been achieved via the semioxamazones of ketone 2.
Pseudosugars, 35. Synthesis of glycosylceramide analogs composed of imino‐linked unsaturated 5a‐carbaglycosyl residues: Potent and specific gluco‐ and galactocerebrosidase inhibitors
Authors: Tsunoda Hidetoshi , Inokuchi Jin‐Ichi , Yamagishi Kiwamu , Ogawa Seiichiro 
Published: July 2007

Abstract5a‐Carba‐β‐glucosyl‐ E‐3 and galactosylceramide analogs E‐4 were synthesized by coupling of the protected derivatives 5 of β‐valienamine and 15 of 4‐epi‐β‐valienamine with the aziridines E‐6 and Z‐6, as the sphingosine precursors, respectively, and subsequent deprotection and N‐acylation. Both the new analogs and their corresponding Z‐isomers Z‐3 and Z‐4 were shown to be very potent and specific gluco‐ and galactocerebrosidase inhibitors, and, interestingly, the Z‐isomers possess inhibitory activity comparable to that of the corresponding E‐isomers.
Azo bridges from azines, XIV. Rigid polycycles with NN and CC functionalities
Authors: Hünig Siegfried , Kraft Petra , Klarner Frank‐Gerrit , Artschwanger‐Perl Uwe , Peters Karl , Von Schnering Hans‐Georg 
Published: July 2007

AbstractBifunctional 9, 3, 17, and trifunctional 20 dienophiles have been subjected to Diels‐Alder reactions with 4H‐pyrazoles 8 or 14 with inverse electron demand to form monoadducts 13, 15, 18, and 21 and bisadducts 16, 19, and 26. Acid‐catalyzed reactions at 20°C occur according to 14 + 3 → 15 + 16 and 14 + 17 → 18 + 19. By contrast, the solution of barrelene (20) and 8 has to be subjected to 10 kbar and 130°C to give monoadduct 21 and bisadduct 26, In daylight 21 undergoes [2 + 2] cycloaddition to 27. The norbornene derivative 10 reacts with cyclopentadiene to form 13 which is obtained in higher yield by reaction of 10 with hexachlorocyclopenta‐diene and subsequent reductive dehalogenation of adduct 12. X‐ray analyses of 11 and 13 reveal only small differences in the structural parameters.
2,7,9‐trimethylenetricyclo[4.3.0.03,8]nonane and 2,9‐dimethylenetricyclo[4.3.0.03,8]non‐4‐ene. Synthesis and properties
Authors: Gleiter Rolf , Herb Thilo , Borzyk Oliver , Hyla‐Kryspin Isabella 
Published: July 2007

AbstractThe synthesis of 2,7,9‐trimethylenetricyclo[4.3.0.03,8]nonane (8), 7,9‐dimethylenetricyclo[4.3.0.03,8]nonan‐2‐one (15), and 2,9‐dimethylenetricyclo[4.3.0.03,8]non‐4‐ene (9) has been achieved. The first key step of the synthesis is a Diels‐Alder reaction. In the reaction sequence affording 8 and 15 the starting materials are 1,3‐cyclohexadiene (10) and acetylallene (11) and in the synthesis of 9 the diene 16 and methyl vinylketone (17). Further key steps are an intramolecular Paterno‐Büchi and an oxetane ring‐opening reaction. Compound 8 as well as 15 rearrange to the corresponding triquinane derivatives according to a Cope rearrangement. The PE spectra of 8, 9, and 15 reveal a considerable through‐space and through‐bond interaction of the double bonds.
Enantioselective synthesis of bis(γ‐butyrolactones). Their oxidative degradation to tetraols as a key step in stereoselective syntheses of 1,3,5,7,9‐pentaol synthons for polyhydroxylated natural products
Authors: Menges Markus , Brückner Reinhard 
Published: July 2007

AbstractThe syntheses of two enantiopure skipped‐chain pentaol building blocks 51 and 56 are described. They are based on a strategy which derives 1,3,7,9‐tetraols from bis (γ‐butyrolactones). Two equivalents of γ‐lactone 17, readily available from L‐glutamic acid, and one equivalent of the diiodoisobutene 22 furnished bis(γ‐butyrolactone) trans,trans‐21 stereoselectively in a single step. The same lactone, combined in a 2:1 ratio with the dibromoisobutene derivative 18, led in four steps and with good stereocontrol to the isomeric bis(γ‐lactone) cis,trans‐21. On the basis of the 1H‐ and 13C‐NMR spectral data of these and other lactones it was possible to distinguish 1,3‐cis‐ and 1,3‐trans‐disubstituted γ‐lactones. Each of the bislactones was subject to a Criegee rearrangement of derived bis(peroxosulfonates) to give the diastereomerically pure 1,3,7,9‐tetraols 26 and 31. The configuration of these tetraols was proven by the 13C‐NMR shifts of the corresponding bis(acetonides) 27 and 32. Ozonolytic cleavage of the CC bond of 27, reduction of the obtained ketone 28 to alcohol 29, acetonide rearrangement under thermodynamic control (→ 30), and fuctionalization of the liberated hydroxy group delivered the end group‐differentiated 1,3,5,7,9‐pentaol building block 51. It represents a segment of the polyol parts of the antibiotics roxaticin (52) and mycoticin (53). The oxidative cleavage of the CC bond of bis(acetonide) 32 and chelation‐controlled reduction of the resulting ketone 33 with Zn(BH4)2 furnished after acetonide migration and functionalization of the unprotected hydroxy group the all‐syn‐configured 1,3,5,7,9‐pentaol building block 56. The latter compound should provide an entry into total syntheses of the naturally occurring poly(methyl ethers) 57 and 58.
Glycosyl imidates, 70. Synthesis of a coumarin C‐glucoside
Authors: Mahling Jürgen‐Andreas , Schmidt Richard R. 
Published: July 2007

Abstract3,5‐Dimethoxyphenol (2) was glycosylated with O‐(2,3,4,6‐tetra‐O‐benzyl‐α‐D‐glucopyranosyl) trichloroacetimidate (1) and trimethylsilyl triflate (TMSOTf) as the promoter to yield the aryl C‐glycoside 3 via an O‐glycoside intermediate and subsequent Fries rearrangement. After formylation, the coumarin C‐glycoside 7 was synthesized either by Perkin reaction with acetic anhydride or by Wittig reaction followed by cyclization at 150°C. Deprotonation yielded the coumarin 8‐C‐glycoside 8, a dimethyl ether of an isomer of naturally occurring coumarin 6‐C‐glycosides.
Reactions of cyclic oxalyl compounds, 37. Substituent effects on the site of nucleophilic attack at 1H‐pyrrole‐2,3‐diones
Authors: Kappe C. Oliver , Terpetschnig Ewald , Penn Gerhard , Kollenz Gert , Peters Karl , Peters Eva‐Maria , von Schnering Hans Georg 
Published: July 2007

AbstractReactions of 1H‐pyrrole‐2,3‐diones 2a‐i with N‐ and O‐nucleophiles proceed by initial attack at C‐2 or/and C‐5. Consequently, earlier results suggesting structures of type A (attack at C‐3) have to be revised (5, 13, 17, 18b). In general, electron‐withdrawing substituents at C‐4 favor attack at C‐5 with formation of 2‐pyrrolones 5, 6, 10, 13, 17, and 20. Alternatively, attack at C‐2 leads to α‐oxobutenoic acid derivatives 3, 7, 11, 12, 15, and 18. IR and 13C‐NMR spectroscopic techniques were employed to differentiate between the possible isomeric addition products formed. The structure of methyl α‐oxobutenoate 15 was established by an X‐ray crystallo‐graphic analysis.
Neue Synthese von 4‐Azaphenothiazin
Authors: Kutscher Bernhard , Dieter Hans Reinhold , Trömer Hans‐Günther , Bartz Beate , Engel Jürgen , Kleemann Axel 
Published: July 2007

New Synthesis of 4‐AzaphenothiazineHerrn Dr. W. A. Schuler zum 80. Geburtstag gewidmet.
The reaction of 2‐chloropyridine with 2‐aminothiophenol gives N‐(2‐mercaptophenyl)‐2‐pyridinamine (2) which is cyclised to give 4‐azaphenothiazine (3), a useful intermediate for pharmaceuticals. An improved one‐pot synthesis is reported and a reaction mechanism proposed.
Stereoselective Synthesis of (E)‐Tagetone
Authors: Kunz Joachim , Breitmaier Eberhard 
Published: July 2007

Abstract(E)‐Tagetone (8) was prepared in four steps by successive alkylation of 1,3‐dithiane (1) by 1‐iodo‐2‐methylpropane (2) and by 3‐ethoxy‐2‐methylacrolein (3), followed by treatment of the intermediate 4 with sulfuric acid. Wittig alkylenation of the resulting aldehyde 5 and removal of the protecting group affords the title compound in good yield.
The synthesis of rac‐peniolactol and some related compounds
Authors: Rama Nasim H. , Saeed Aamer , Bird Clive W. 
Published: July 2007

AbstractThe structure (±)‐3,6,8‐trihydroxy‐3‐pentadecyl‐3,4‐dihydroisocoumarin 1 assigned by earlier workers to peniolactol, a metabolite of Peniophora sanguinea, has been confirmed by total synthesis of this compound and some of its derivatives.
Cyclization reactions of tricarbonylmethane thiosemicarbazones: Formation of 1,3,4‐thiadiazole derivatives with concomitant CC bond cleavage
Authors: Somogyi László 
Published: July 2007

AbstractUnder acylating conditions 3‐acetyl‐4‐hydroxy‐2H‐pyran‐2‐one thiosemicarbazones (1a, b and 2a, b) are transformed into 2‐(acylamino)‐5‐methyl‐1,3,4‐thiadiazoles 3b, c, e, f and 2H‐pyran‐2‐ones 1c and 2c via C–C bond cleavage. Similarly, the reaction of 1b with RCO2H/EtOH (R = Me, Et) affords 2‐anilino‐5‐methyl‐1,3,4‐thiadiazole (3d) and triacetic acid lactone 1c. Upon treatment with Ac2O/Et3N the dehydroacetic acid derivative 1b is transformed into the thiadiazoline 4, while the benzo derivative 2b is converted into thiadiazole 3e and 4‐acetoxycoumarin (2c).
A Short Synthesis of a Thromboxane B2 Key Intermediate from (R)‐2,3‐Isopropylideneglyceraldehyde. γ‐Lactones as Templates for Chemoselective cis‐Annulation of Pyranosides
Authors: Mulzer Johann , Graske Klaus‐Dieter , Shanyoor Mazin 
Published: July 2007

AbstractA six‐step synthesis of the bicyclic lactone pyranoside 1, which has served as a key intermediate in numerous syntheses of thromboxane B2, from (R)‐2,3‐isopropylideneglyceraldehyde is described. In contrast to the previous syntheses of 1 the lactone part is prepared first and acts as a template in the annulation of the hemiketal unit. Further aspects of interest are the Felkin‐Anh‐controlled addition of vinyl cuprates to the acrylic ester 16 and the considerable rate difference in the formation of the γ‐lactones 13, 14, 19, and 21 from the corresponding hydroxy acids.
Photochemistry of di‐Schiff bases and related compounds
Authors: Tauer Erich , Grellmann Karl‐Heinz , Heinrich Angelika 
Published: July 2007

AbstractThe photochemical properties of the di‐Schiff base 2 have been investigated. The first reaction step of 2 in 2‐propanol or in cyclohexane is an intramolecular photoreductive coupling affording the diazocine meso‐4. Subsequent photoreactions of meso‐4 in 2‐propanol are studied. In concentrated solutions of phenanthridine in cyclohexane a photodimerization takes place during which two CH bonds are broken and two NH bonds are formed. The photodimer reconverts with high quantum yield quantitatively to the monomer.
Synthesis of sphingosines, 11. Convenient synthesis of phytosphingosine and sphinganine fromD‐galactal andD‐arabitol
Authors: Wild Robert , Schmidt Richard R. 
Published: July 2007

Abstract3,4,6‐Tri‐O‐benzyl‐D‐galactal (3) was directly converted into 3,4,6‐tri‐O‐benzyl‐2‐deoxy‐D‐galactose (5). Wittig reaction of5with alkyltriphenylphosphonium salts in the presence ofn‐butyllithium as the base afforded olefins6a, bwhich could be readily transformed into phytosphingosines1a, bvia different routes: (i) at first azido group introduction and then double bond and protective group removal, and azido group generation via hydrogenation; (ii) 2‐O‐mesylation, then double bond and benzyl group removal via hydrogenation, and finally nitrogen introduction; (iii) selective double bond hydrogenation, then nitrogen introduction, and finally benzyl group removal and amino group generation via hydrogenation. Wittig reaction of5with alkyltriphenylphosphonium salt in the presence of potassiumtert‐butoxide as the base afforded diene7awhich proved to be a convenient precursor for sphinganine syntheses; thus, 2‐O‐mesylation, then double bond and benzyl group removal via hydrogenation and 1,3‐O‐acetylation, and finally nitrogen introduction and de‐O‐acetylation afforded23a.Based on the convenient transformation of D‐arabitol into the 1,3‐O‐benzylidene derivative25a further phytosphingosine synthesis is outlined.
Simple and condensed β‐lactams, XIX. Synthesis Of some new 7‐acylamino‐2‐iso‐oxacephem‐4‐carboxylic acids
Authors: Tombor Zoltán , Greff Zoltán , Nyitrai József , Kajtár‐Peredy Mária 
Published: July 2007

AbstractGeneral methods have been developed for the synthesis of 7‐amino‐2‐iso‐oxacephem‐4‐carboxylic acid esters 21a,b; 35b. Clayfen [Fe(III) nitrate supported by montmorillonite] was used for the preparation of benzyl 2,3‐dioxobutyrate (3). The latter readily reacted with N(1)‐unsubstituted β‐lactams (9a, 28) to give products formed by addition reaction on the middle carbonyl‐C atom. These intermediates furnished the corresponding acetoacetic esters 10, 29 which gave by ring closure the O‐mono‐ and the O,N‐diprotected‐2‐iso‐oxacephems (11, 30). Intermolecular carbene insertion was used for the synthesis of tert‐butyl 2‐(2‐oxoazetidin‐1‐yl)acetoacetates 19a,b whose ring closure led to the tert‐butyl 2‐iso‐oxa‐cephem‐4‐carboxylates 20a,b. The O‐protecting tert‐butyl group could be removed without decomposition of the 2‐isooxacephem moiety to give 2‐iso‐oxacephem‐4‐carboxylic acids 2a,b which exhibit antibacterial activity against Grampositive microorganisms.
Substituent effects on the CC bond strength, 18. Stabilization of alkyl radicals by 4‐pyridyl, 1‐naphthyl or 2‐naphthyl substituents in α‐position
Authors: Herberg Clemens , Peyman Anuschirwan , Nölke Margot , Beckhaus Hans‐Dieter , Rüchardt Christoph 
Published: July 2007

AbstractThe formation of the α‐substituted radicals 7–9 with the 4‐pyridyl (7), 1‐naphthyl (8), and the 2‐naphthyl (9) substituent by thermolysis of their dimers 1–3 in solution was investigated. The activation parameters of the homolysis of the central CC bond were obtained from kinetic measurements of the thermal cleavage of 1–3 in the presence of radical scavengers. These data were compared with those obtained from the thermolysis of alkanes which cleave into α‐alkyl branched radicals, and which lose the same amount of strain during the dissociation. The „strain‐free”︁ radical stabilization enthalpies of the α‐substituted radicals [RSE = 7.9 ± 1.8 (7), 12.0 ± 1.4 (8), and 8.7 ± 1.9 kcal/mol (9)] were obtained in this way.
Syntheses and CD studies of 5α‐cholesteno[3,2‐d]‐, ‐[2,3‐d]‐ and ‐[3,4‐d]pyrimidines
Authors: Hasan Mashooda , Rashid Naghmana , Khan Khalid Mohammed , Snatzke Günther , Duddeck Helmut , Voelter Wolfgang 
Published: July 2007

AbstractSyntheses of 5α‐cholesteno[3,2‐d]‐ (5a), [2,3‐d]‐ (12a), and [3,4‐d]pyrimidines (15a) have been achieved by using hydroxymethylene derivatives of relevant cholestanones prepared from cholesterol (1). Their CD spectra exhibit at least three Cotton effects between 300 to 200 nm, a first CD band around 290, a second one around 260 and a third one around 220 nm. A quadrant rule is developed and applied to the determination of the sign of the first CD band, while a helicity rule is applicable to the third CD band. The first band is positive in the [3,2‐d] series, whereas it is negative in the [2,3‐d] and the [3,4‐d] series. The third band is negative in all three series.