Mass spectra of some α-substituted phenyl-α,α′-dimethoxyl ketones and their derivatives

The mass spectra of some α-substituted phenyl-α,α′-dimethoxyl ketones (compounds 1) and their 2,4-dinitrophenylhydrazones (compounds 2) and semicarbazones (compounds 3) have been studied. The characteristic fragments at m/z (M ? 73) from compounds 1, m/z (M ? 253) from compounds 2 and m/z (M ? 130) from compounds 3 are abundant and proposed to be [ArCROCH₃]⁺. Fragmentations yielding [M⁺ ? 49] from compounds 2 are abnormal and probably involve the methoxyl and nitro groups. The intense peak at m/z 130 due to [CH₃OCH₂CNNHCONH₂]⁺ from compounds 3 corresponds to α-cleavage of the molecular ion. Some other fragments from these new compounds are interpreted in this paper.     

The Crystal and Molecular Structure of 3-Oxo-17β-acetoxy-Δ4-14α-methyl-8α, 9β, 10α, 13α-estrene

The crystal and molecular structure of 3-oxo-17β-acetoxy-Δ⁴-14α-methyl-8α, 9β, 10α, 13α-estrene, C₂₁H₃₀O₃, has been determined by X-ray diffraction analysis. The crystals belong to the orthorhombic space group P2₁2₁2₁, with the cell dimensions a = 12.093 Å, b = 19.667 Å, c = 7.746 Å; Z = 4. Intensity data were collected at room temperature with an automatic four-circle diffractometer. The structure was solved by direct methods and the parameters were refined by least-squares analysis. All the hydrogen atoms were included in the refinement. The final R value was 0.038 for 1413 observed reflections. The conformation of ring A is intermediate between a half-chair and a 1, 2-diplanar form. The hydrogens at C(9) and C(10) are anti, the B/C ring junction is trans, and rings B and C adopt chair conformations. Ring D is cis fused and is halfway between C₂ and C_s forms.     

Thermische Lactonisierung von Estern γ-Brom-α, β-ungesättigter Carbonsäuren zu Δα-Butenoliden. Direkte γ-Bromierung von α, β-ungesättigten Säuren

By heating with iron powder at 120–150° some γ-bromo-α, β-unsaturated carboxylic methyl esters, and, less smothly, the corresponding acids, were lactonized to Δ^7alpha;-butenolides with elimination of methyl bromide. The following conversions have thus been made: methyl γ-bromocrotonate ( 1c ) and the corresponding acid ( 1d ) to Δ^α-butenolide ( 8a ), methyl γ-bromotiglate ( 3c ) and the corresponding acid ( 3d ) to α-methyl-Δ^α-butenolide ( 8b ), a mixture of methyl trans- and cis-γ-bromosenecioate ( 7c and 7e ) and a mixture of the corresponding acids ( 7d and 7f ) to β-methyl-Δ^α-butenolide ( 8c ). The procedure did not work with methyl trans-γ-bromo-Δ^α-pentenoate ( 5c ) nor with its acid ( 5d ). Most of the γ-bromo-α, β-unsaturated carboxylic esters ( 1c, 7c, 7e and 5c ) are available by direct N-bromosuccinimide bromination of the α, β-unsaturated esters 1a, 7a and 5a ; methyl γ-bromotiglate ( 3c ) is obtained from both methyl tiglate ( 3a ) and methyl angelate ( 4a ), but has to be separated from a structural isomer. The γ-bromo-α, β-unsaturated esters are shown by NMR. to have the indicated configurations which are independent of the configuration of the α, β-unsaturated esters used; the bromination always leads to the more stable configuration, usually the one with the bromine-carrying carbon anti to the carboxylic ester group; an exception is methyl γ-bromo-senecioate, for which the two isomers (cis, 7e , and trans, 7d ) have about the same stability. The N-bromosuccinimide bromination of the α,β-unsaturated carboxylic acids 1b , 3b , 4b , 5b and 7b is shown to give results entirely analogous to those with the corresponding esters. In this way γ-bromocrotonic acid ( 1 d ), γ-bromotiglic acid ( 3 d ), trans- and cis-γ-bromosenecioic acid ( 7d and 7f ) as well as trans-γ-bromo-Δ^α-pentenoic acid ( 5d ) have been prepared. Iron powder seems to catalyze the lactonization by facilitating both the elimination of methyl bromide (or, less smoothly, hydrogen bromide) and the rotation about the double bond. α-Methyl-Δ^α-butenolide ( 8b ) was converted to 1-benzyl-( 9a ), 1-cyclohexyl-( 9b ), and 1-(4′-picoly1)-3-methyl-Δ^α-pyrrolin-2-one ( 9 c ) by heating at 180° with benzylamine, cyclohexylamine, and 4-picolylamine. The butenolide 8b showed cytostatic and even cytocidal activity; in preliminary tests, no carcinogenicity was observed. Both 8b and 9c exhibited little toxicity.     

Nonreductive Enantioselective Ring Opening of N-(Methylsulfonyl)dicarboximides with Diisopropoxytitanium α,α,α′,α′-Tetraaryl-1,3-dioxolane-4,5-dimethanolate

The bicyclic and tricyclic meso-N-(methylsulfonyl)dicarboximides 1a–f are converted enantioselectively to isopropyl [(sulfonamido)carbonyl]-carboxylates 2a–f by diisopropoxytitanium TADDOLate (75–92% yield; see Scheme 3). The enantiomer ratios of the products are between 86:14 and 97:3, and recrystallization from CH₂Cl₂/hexane leads to enantiomerically pure sulfonamido esters 2 (Scheme 3). The enantioselectivity shows a linear relationship with the enantiomer excess of the TADDOL employed (Fig.3). Reduction of the ester and carboxamide groups (LiAlH₄) and additional reductive cleavage of the sulfonamido group (Red-Al) in the products 2 of imide-ring opening gives hydroxy-sulfonamides 3 and amino alcohols 4 , respectively (Scheme 4). The absolute configuration of the sulfonamido esters 2 is determined by chemical correlation (with 2a,b ; Scheme 6), by the X-ray analysis of the camphanate of 3e (Fig. 1), and by comparative ¹⁹F-NMR analysis of the Mosher esters of the hydroxy-sulfonamides 3 (Table 1). A general proposal for the assignment of the absolute configuration of primary alcohols and amines of Formula HXCH₂CHR¹R², X = O, NH, is suggested (see 11 in Table 1). It follows from the assignment of configuration of 2 that the Re carbonyl group of the original imide 1 is converted to an isopropyl ester group. This result is compatible with a rule previously put forward for the stereochemical course of reactions involving titanium TADDOLate activated chelating electrophiles ( 12 in Scheme 7). A tentative mechanistic model is proposed ( 13 and 14 in Scheme 7).     

Kinetics of the reactions of cyclopropane derivatives. V. The gas-phase unimolecular reactions of 1 α-chloro-2α,3α-dimethylcyclopropane and 1α-chloro-2α,3β-dimethylcyclopropane

Thermolysis of the “all-cis” compound 1α-chloro-2α,3α-dimethylcyclopropane (A) at 550–607 K and 6–115 torr is a first-order homogeneous non-radical-chain process giving penta-1,3-diene (PD) and HCl as products. The Arrhenius parameters are log₁₀A(sec^?1) = 13.92 ± 0.08 and E = 199.6 ± 0.9 kJ/mol. The isomer with trans-methyl groups, 1α-chloro-2α,3β-dimethylcyclopropane (B) reacts by two parallel first-order processes giving as observed products trans-4-chloropent-2-ene (4CP) and PD + HCl, with log₁₀A(sec^?1) = 14.6 and 13.8, respectively, and E = 199.5 and 190.2 kJ/mol, respectively. The 4CP undergoes secondary decomposition to PD + HCl (as investigated previously). Comparison of the results for compounds (A) and (B) with those for other gas-phase and solution reactions leads to the conclusion that the gas-phase thermolyses proceed by rate-determining ring opening to form olefins which may decompose further by thermal or chemically activated reactions, and that the ring opening is a semiionic electrocyclic reaction in which alkyl groups in the 2,3-positions trans to the migrating chlorine semianion move apart, with appropriate consequences for the rate of reaction and the stereochemistry of the products.     

Synthesis of Some Novel Phenyl Substituted Oxothiazolidin- 1’’,3’’,4’’-thiadiazolo-[3’,4’-b]thiazoline of 3β-Substituted Cholestane

Three title compounds 4a—4c have been synthesized by the cyclodehydration of 1’-benzylidine-4’-(3β-substituted-5α-cholestane-6-yl)thiosemicarbazones 2a—2c with thioglycolic acid followed by the treatment with cold conc. H2SO4 in dioxane. The compounds 2a—2c were prepared by condensation of 3β-substituted-5α-cholestan- 6-one-thiosemicarbazones 1a—1c with benzaldehyde. These thiosemicarbazones 1a—1c were obtained by the reaction of corresponding 3β-substituted-5α-cholestan-6-ones with thiosemicarbazide in the presence of few drops of conc. HCl in methanol. The structures of the products have been established on the basis of their elemental, analytical and spectral data.     

20, 21-Azirdin-Steroide: Reaktion von Derivaten der Oxime von 5-Pregnen-20-on,9β,10α-5-Pregnen-20-on und 9β,10α-5,7-Pregnadien-20-on mit Lithiumaluminiumhydrid und von 3β-Hydroxy-5-pregnen-20-on-oxim mit Grignard-Verbindungen

20, 21-Aziridine Steroids: Reaction of Derivatives of the Oximes of 5-Pregnen-20-one, 9β, 10α-5-Pregnen-20-one and 9β, 10α-5,7-Pregnadiene-20-one with Lithium Aluminium Hydride, and of 3β-Hydroxy-5-pregnen-20-one Oxime with Grignard Reagents. Reduction of 3β-hydroxy-5-pregnen-20-one oxime ( 2 ) with LiAlH₄ in tetrahydrofuran yielded 20α-amino-5-pregnen-3β-ol ( 1 ), 20β-amino-5-pregnen-3β-ol ( 3 ), 20β, 21-imino-5-pregnen-3β-ol ( 6 ) and 20β, 21-imino-5-pregnen-3β-ol ( 9 ). The aziridines 6 and 9 were separated via the acetyl derivatives 7 and 10 . The reaction of 6 and 9 with CS₂ gave 5-(3β-hydroxy-5-androsten-17β-yl)-thiazolidine-2-thione ( 8 ). Treatment of the 20-oximes 12 and 15 of the corresponding 9β,10α(retro)-pregnane derivatives with LiAlH₄ gave the aziridines 13 and 16 , respectively. Their deamination led to the diene 14 and triene 17 , respectively. Reduction of isobutyl methyl ketone-oxime with LiAlH₄ in tetrahydrofuran yielded 2-amino-4-methyl-pentane ( 19 ) as main product, 1, 2-imino-4-methyl-pentane ( 22 ) as second product and the epimeric 2,3-imino-4-methyl-pentanes 20 and 21 as minor products. – 3β-Hydroxy-5-pregnen-20-one oxime ( 2 ) was transformed by methylmagnesium iodide in toluene to 20α, 21-imino-20-methyl-5-pregnen-3β-ol ( 23 ) and 20β, 21-imino-20-methyl-5-pregnen-3β-ol ( 26 ). Acetylation of these aziridines was accompanied by elimination reactions leading to 3β-acetoxy-20-methylidene-21-N-acetylamino-5-pregnene ( 30 ) and 3β-acetoxy-20-methyl-21-N-acetylamino-5,17-pregnadiene ( 32 ). The reaction of oxime 2 with ethylmagnesium bromide in toluene gave 20α, 21-imino-20-ethyl-5-pregnen-3β-ol ( 24 ) and 20α,21-imino-20-ethyl-5-pregnen-3β-ol ( 27 ). Acetylation of 24 and 27 led to 3β-acetoxy-20-ethylidene-21-N-acetylamino-5-pregnene ( 31 ), 3β-acetoxy-20-ethyl-21-N-acetylamino-5,17-pregnadiene 33 and 3β, 20-diacetoxy-20-ethyl-21-N-acetylamino-5-pregnene ( 37 ). With phenylmagnesium bromide in toluene the oxime 2 was transformed to 20β, 21-imino-20-phenyl-5-pregnen-3β-ol ( 25 ) and 20β,21-imino-20-phenyl-5-pregnen-3β-ol ( 28 ). Acetylation of 25 and 28 yielded 3β-acetoxy-20-phenyl-21-N-acetylamino-5, 17-pregnadiene ( 34 ) and 3β,20-diacetoxy-20-phenyl-21-N-acetylamino-5-pregnene ( 39 ). LiAlH₄-reduction of 39 gave 3β, 20-dihydroxy-20-phenyl-21-N-ethylamino-5-pregnene ( 41 ). – The 20, 21-aziridines are stable to LiAlH₄. Consequently they are no intermediates in the formation of the 20-amino derivatives obtained from the oxime 2 .     

Lipophilic Functionalized Cobyrinic-Acid Derivatives. Part 1. Cobester α-monoacids (α,α,α,β,β,β-hexamethyl α-hydrogen Coα, Coβ-dicyanocobyrinates)

The four α,α,α, β,β,β,-hexamethyl α-hydrogen Coα, Coβ-dicyanocobyrinates 2b, d–f , with a free b-, d-, e-, and f-propionic-acid function, respectively, were prepared by partial hydrolysis of heptamethyl Coα, Coβ-dicyanocobyrinate (cobester; 1 ) in aqueous sulfuric acid. The cobester monoacids 2b, d–f were obtained as a ca. 1:1:1:1 mixture which was separated. The monoacids were purified by chromatography and isolated in crystalline form. The position of the free propionic-acid function was determined by an extensive analysis of 2b, d–f using 2D-NMR techniques; an analysis of the C,H-coupling network topology resulted in an alternative assignment strategy for cobyrinic-acid derivatives, based on pattern recognition. Additional information on the structure of the most polar of the four hexamethyl cobyrinates, of the b-isomer 2b , was also obtained in the solid state from a single-crystal X-ray analysis. Earlier structural assignments based on 1D-NMR spectra of the corresponding regioisomeric monoamides 3b, d–f (obtained from crystalline samples of the monoacids 2b, d–f ) were confirmed by the present investigations.     

Stereochemistry of Formation of the β‐Ring of Lycopene: Biosynthesis of (1R,1′R)‐β,β‐[16,16,16,16′,16′,16′‐2H6]Carotene from [16,16,16,16′,16′,16′‐2H6]Lycopene in Flavobacterium R 1560

Incubation of deuteriated precursors in cultures of Flavobacterium produced specifically deuteriated carotenoids. Analysis of these led to several conclusions: i) Lycopene is a direct precursor of β,β‐carotene. ii) Its terminal Me groups retain their integrity during cyclization: there is a stereospecific folding of the 1,5‐diene. The Me(16,16′) groups of lycopene become the Me(16,16′) of β,β‐carotene. Consequently, the folding must follow the C₂(E,E) mode. iii) Incorporation of deuterium was sufficiently extensive to permit CD measurements on the isolated β,β‐carotene, allowing its centers of chirality to be assigned as (1S,1′S). iv) The same chirality resulted from incorporation of [²H₃]mevalonate into zeaxanthin. The syntheses of specifically deuteriated [²H₃]GPP, [²H₃]FPP, and [²H₃]GG are described.     

Angiotensin-II Analogues. I: Synthesis and incorporation of the halogenated amino acids 3-(4′-iodophenyl)alanine, 3-(3′,5′-dibromo-4′-chlorophenyl)alanine, 3-(3′,4′,5′-tribromophenyl)alanine,and 3-(2′,3′,4′,5′,6′-pentabromophenyl)alanine

The synthesis of the polyhalogenated phenylalanines Phe(3′,4′,5′-Br₃) ( 3 ), Phe(3′,5′-Br₂-4′-Cl) ( 4 ) and DL -Phe (2′,3′,4′,5′,6′-Br₅) ( 9 ) is described. The trihalogenated phenylalanines 3 and 4 are obtained stereospecifically from Phe(4′-NH₂) by electrophilic bromination followed by Sandmeyer reaction. The most hydrophobic amino acid 9 is synthesized from pentabromobenzyl bromide and a glycine analogue by phase-transfer catalysis. With the amino acids 4, 9 , Phe(4′-I) and D -Phe, analogues of [1-sarcosin]angiotensin II ([Sar¹]AT) are produced for structure-activity studies and tritium incorporation. The diastereomeric pentabromo peptides L - and D - 13 are separated by HPLC. and identified by catalytic dehalogenation and comparison to [Sar¹]AT ( 10 ) and [Sar¹, D -Phe⁸]AT ( 14 ).     

Destabilized carbenium ions: α-carbomethoxy-α,α-dimethyl-methyl cations

Tertiary α-carbomethoxy-α,α-dimethyl-methyl cations a have been generated by electron impact induced fragmentation from the appropriately α-substituted methyl isobutyrates 1–4. The destabilized carbenium ions a can be distinguished from their more stable isomers protonated methyl methacrylate c and protonated methyl crotonate d by MIKE and CA spectra. The loss of I^— and Br˙ from the molecular ions of 1 and 2, respectively, predominantly gives rise to the destabilized ions a, whereas loss of Cl˙ from [3]^{+ ˙} results in a mixture of ions a and c. The loss of CH₃˙ from [4]⁺˙ favours skeletal rearrangement leading to ions d. The characteristic reactions of the destabilized ions a are the loss of CO and elimination of methanol. The loss of CO is associated by a very large KER and non-statistical kinetic energy release (T₅₀ = 920 meV). Specific deuterium labelling experiments indicate that the α-carbomethoxy-α,α-dimethyl-methyl cations a rearrange via a 1,4-H shift into the carbonyl protonated methyl methacrylate c and eventually into the alkyl-O protonated methyl methacrylate before the loss of methanol. The hydrogen rearrangements exhibit a deuterium isotope effect indicating substantial energy barriers between the [C₅H₉O₂]⁺ isomers. Thus the destabilized carbenium ion a exists as a kinetically stable species within a potential energy well.     

Dissimilar behaviour of 3β, 16α-dihydroxy-5α-androstan-17-one Diacetate under Basic and Acidic Conditions

The base-catalysed rearrangement of 3β, 16α-dihydroxy-5α-androstan-17-one diacetate ( 1 ) in (D₆)benzene/ CD₃OD to 3β, 17β-dihydroxy-5α-androstan-16-one ( 3 ) is followed by ¹³C-NMR spectroscopy. By the same procedure, it is determined that in (D₆)benzene/CD₃OD, but under acid catalysis, 1 does not rearrange to 3 but yields the intermediate product 3β, 16α-dihydroxy-5α -androstan-17-one 17α -methyl hemiacetal ( 5 ).     

Selektive Amidspaltung bei Peptiden mit α,α-disubstituierten α-Aminosäuren

Selective Amide Cleavage in Peptides Containing α,α-Disubstituted α-Amino Acids A new synthesis of dipeptides with terminal α,α-disubstituted α-amino acids, using 2,2-disubtituted 3-amino-2H-azirines 1 as amino-acid equivalents, is demonstrated. The reaction of 1 with N-protected amino acids leads to the corresponding dipeptide amides in excellent yield. It is shown that the previously described selective hydrolysis (HCl, toluene, 80°, or HCl, MeCN/H₂O, 80°) of the terminal amide group results in an extensive epimerization of the second last amino acid. An acid-catalyzed enolization in the intermediate oxazole-5(4H)-ones is responsible for this loss of configurational integrity. In the present paper, a selective hydrolysis of the terminal amide group under very mild conditions is described: In 3_N HCl (THF/H₂O 1:1), the dipeptide N,N-dimethylamides or N-methytlanilides are hydrolized at 25–35° to the optically pure dipeptides in very good yield.     

Isolierung von 11α, 11′α-Dihydroxychaetocin aus Verticillium tenerum

Based on ¹³C-NMR. and other physico-chemical evidence, the structure of 11α, 11′α-dihydroxychaetocin ( 3 ) has been assigned to a new antibacterial and antimitotic metabolite, isolated from the fungus Verticillium tenerum.     

Pterin Chemistry. Part 92.. Loading experiments with 6α,β-tetrahydro-L-[3′-2H1] biopterin

6α,β-Tetrahydro-L -[3′-²H₁]biopterin ([3′-²H₁]- 1 ) was administered orally to two primapterinuric patients in order to investigate the biosynthetic pathway of 7-substituted pterins in humans. L -Primapterin ( 2 ) and L -biopterin were isolated from urine after loading and measured by GC/MS. L -Biopterin and L -primapterin were labelled with ²H to an equal extent. From this result, one can conclude that L -primapterin is formed from tetrahydro-L -biopterin, very probably via an intramolecular rearrangement.     

Effect of tin tetrachloride on thermal decompositions of α,α′-azobisisobutyronitrile and dimethyl α,α′-azobisisobutyrate

Thermal decomposition of α,α′-azobisisobutyronitrile (AIBN) and dimethyl α,α′-azobisisobutyrate (MAIB) in the presence of a large amount of tin tetrachloride was investigated to determine the effect of complex formation on the decomposition rates and yields of the recombination products. The addition of tin tetrachloride significantly increased the decomposition rates; the observed first-order rate constant increased by factors of 4.5 and 17 at molar ratios of [SnCl₄]/[AIBN] = 21.65 and [SnCl₄]/[MAIB] = 19.53, respectively. It was found that the decomposition of these azo compounds was also accelerated by the addition of a comparable amount of donor solvent such as ethyl acetate or propionitrile to tin tetrachloride and that the enhancement in rate was accounted for by a larger frequency factor in the Arrhenius equation. Furthermore, the addition of tin tetrachloride seemed to suppress the formation of recombination products, tetramethyl succinonitrile and dimethyl tetramethylsuccinate, of the radicals produced by decomposition.     

α-D-Glycosyl-Substituted α,α-D-Trehaloses with (1 → 4)-Linkage: Syntheses and NMR Investigations

Two symmetrical trehalose glycosyl ‘acceptors’ 4 and 6 were prepared and three of the unsymmetrical type, 8 , 10 , and 11 . Glucosylation of symmetrical ‘acceptor’ 4 gave a higher yield of trisaccharide (44%) than protect ve-group manipulation, namely via selective debenzylidenation 2 → 9 or monoacetylation 2 → 5 which proceeded in moderate yields (33–34%). A comparison of catalysts in the cis-glucosylation of trehalose ‘acceptor’ 10 with tetra-O-benzyl-β-D -glucopyranosyl fluoride 13 profiled triflic anhydride ((Tf)₂O) as a new reactive promoter yielding 92% of trisaccharide 14 , deblocking gave the target saccharide α-D -glucopyranosyI-( 1 → 4 )-α,α-D -trehalose. ¹H-NMR spectra of most compounds were analyzed extensively. The use of the ID TOCSY technique is advocated for its time efficiency, if needed supplemented by ROESY experiments.     

The reactions of perfluoro- and α,α-dichloropolyfluoroalkanesulfinates

Sodium perfluoroalkanesulfinate, R_FSO₂Na [R_F?Cl(CF₂)₄, 1a; CF₃(CF₂)₅, 1b; Cl(CF₃)₆, 1c] reacted with bromine in aqueous solution to give the corresponding sulfonyl bromide R_FSO₂Br (2a-2c) and in acetonitrile or acetic acid, to form perfluoroalkyl bromide R_FBr (3a-3c). Heating in acetonitrile at 80°C, 2a-2c were converted smoothly into 3a-3c. However, reaction of sodium α,α-dichloropolyfluoroalkanesulfinate RCCl₂SO₂Na (R?CF₃, Cl(CF₂)n, n=2, 4, 6, 5a-5d) with bromine in aqueous solution gave directly the corresponding bromoalkanes 1-bromo-1,1-dichloropolyfluoroalkane RCCl₂Br (6a-6d). In aqueous potassium iodide solution, 1a-1c, 5a and 5b also reacted with iodine to form the corresponding iodo-polyfluoroalkane 4a-4c, 7a and 7b directly. 6a and 7a underwent free radical addition to alkene readily in the presence of free radical initiator and reacted with Na₂S₂O₄ in the usual way to form α,α-dichloropolyfluoroethane sulfinate (5a). 5a was stable in strong acid, but reacted with strong base to yield 10. 5a was oxidised by hydrogen peroxide to the sulfonate 11 and reduced by zinc in dilute acid to from the α-chloro sulfinate 12.     

5α-24-Norcholestan-3β-ol and (24Z)-Stigmasta-5,7,24(28)-trien-3β-ol,Two New Marine Sterols from the Pacific Sponges Terpios zeteki and Dysidea herbacea

The steroidal components of 2 marine sponges, Terpios zeteki (from Hawaii) and Dysidea herbacea (from Australia) were fractionated through a combination of chromatographic methods, including reversed phase HPLC., and were analyzed by a combination of physical methods, including high resolution GC.-MS. and 360 MHz ¹H-NMR. T. zeteki contains 6 conventional 5α-stanols which comprise 91% of the sterol mixture, and traces (0.5%) of a new C₂₆ sterol, 5α-24-norcholestan-3β-ol. Minor amounts of conventional Δ⁵-sterols (6.5%) and of a single Δ⁴-3-ketosteroid (1.5%) were also present. In contrast, the Australian sponge (D. herbacea) contains 3 Δ^5,7-sterols which comprise 1.5% of the sterol mixture, and one new C₂₉ sterol, (24 Z)-stigmasta-5,7,24(28)-trien-3β-ol, as the major component (75%). In addition, minor amounts of conventional 5α-stanols (0.5%), Δ⁵-sterols (5%) and 5α-Δ⁷-sterols (18%) were present in this complex sterol mixture. The possible dietary or endosymbiotic origins of these sterols are discussed.