Muqubilin,a new c24-isoprenoid from a marine sponge

The Red Sea sponge $\text{Prianos}$ sp. contains a cyclic peroxide C₂₄ - nor sesterterpene, Muqubilin ($\text{1}$). The structure of $\text{1}$ was deduced from spectroscopic data and by chemical degradation.     

The structure of zeylasterone - the first of a new series of phenolic 24-nor-D:A-friedo-oleanan triterpenes

Zeylasterone, a new triterpene from Kokoona zeylanica, is shown to be 2,3-dihydroxy-6-oxo-24-nor-D:A-friedo-oleana-1,3,5(10),7-tetraen-23,29-dioic acid-29-methyl ester (20 α) ($\text{1}$), the first member of a new series of phenolic 24-nor-D:A-friedo-oleanans.     

Synthesis of binzindene prostaglandins: a novel potent class of stable prostacyclin analogs

The phenols $\text{13}$, $\text{16}$, and $\text{21}$, produced with remarkable regioselectivity by the cyclization of compounds $\text{10}$ and $\text{12}$, have been converted to the benzindene prostaglandin analogs $\text{25}$, $\text{20}$, and $\text{24}$, respectively. Compounds $\text{24}$ and $\text{25}$ are potent prostacyclin mimics.     

A new steroidal lactone with plant growth-regulatory activity from dolichoslablab seed

A new plant growth-promoting sterol was isolated from immature seeds of $\text{Dolichos}$$\text{labla}$. The structure was elucidated as (22$\text{R}$, 23$\text{R}$-2α, 3α, 22, 23-tetrahydroxy-B-homo-7-oxa-5α-ergost-24(28)-en-6-one $\text{1}$.     

Isolation of sterols with cyclopropyl-containing side chains from the cultured marine alga peridiniumfoliaceum

The sterol fraction of the cultured dinoflagellate $\text{Peridinium}$$\text{foliaceum}$ contains in addition to cholesterol, 24-methylcholesterol, 4,24-dimethylcholesterol and dinosterol ($\text{3c}$) small amounts of the cyclopropyl-containing sterols gorgosterol ($\text{1a}$) and 5α-gorgostanol ($\text{1b}$) as well as 4α-methylgorgostanol ($\text{1c}$) and E-4α,22ξ,23ξ (or 24ξ)-trimethylcholest-17(20)-en-3β-ol ($\text{6c}$ or $\text{7c}$). The biosynthetic implications of the first isolation of such sterols from a free-living alga are emphasized.     

Rates of dediazoniations of arenediazonium ions complexed with 18-, 21- and 24-membered crown ethers

The evaluation of the kinetics of dediazoniation of benzenediazonium tetrafluoroborate and $\text{p}$-chlorobenzenediazonium tetrafluoroborate in 1,2-dichloroethane at 50°C in the presence of 18-crown-6, 21-crown-7 and dicyclohexano-24-crown-8 demonstrates that the rate constant for the dediazoniation within the complex is smallest, and the equilibrium constant for complex formation is largest for the complex with 21-crown-7.     

Four novel C28 sterols from lobophytum depressum

Four novel polyoxygenated C₂₈-sterols have been identified from the soft coral $\text{L. depressum}$ (the Gulf of Eilat, the Red Sea): the 22,28-lactol of 24-methylcholest-5-en-3β,22(R),25-triol-28-al ($\text{1}$), 24-methylcholest-5-en-3β,22(R),25,28-tetraol($\text{2}$) and the corresponding 5,6β-epoxides ($\text{3}$ and $\text{4}$).     

Steroidal antifeedants from the dorid nudibranch Aldisasanguineacooperi

Two steroids, 3-oxo-chol-4-ene-24-oic acid ($\text{2}$) andi ts unsaturated analog $\text{4}$ have been isolated from the dorid nudibranch $\text{Aldisa}$$\text{sanguinea}$$\text{cooperi}$, and the acid $\text{2}$ has been shown to have antifeedant properties.     

New Phenyl propanoids having weak piscicidal action and the related compound: wutaiensol,wutaiensal, wutaialdehyde,and methyl demethoxywutaiensate

The structures of three new prenylphenyl propanoids, wutaiensol ($\text{1}$), wutaiensal ($\text{2}$), and methyl demethoxywutaiensate ($\text{4}$) were established by correlating with S-rutaretin methyl ether ($\text{9}$) or S-marmesin ($\text{24}$) by chemical means. The structure of wutaialdehyde ($\text{3}$), a related compound, was also established by total synthesis of the racemate and by correlating with $\text{1}$. Preliminary piscicidal test on these compounds disclosed that $\text{2}$ and $\text{4}$ are weakly bu distinctly positive.     

Novel synthesis of aza-heterocycles

N-formyl aza-heterocycles $\text{15}$ – $\text{24}$ can be prepared by RaNi desulfirization of thiazolidine derived polycyclics $\text{5}$ – $\text{14}$ which in turn are obtained by intramolecular thiono α-acyliminium cyclisations of π-nucleophiles.     

A general stereocontrolled route to carbocyclic C-nucleosides: (±) carba-showdowmycin

Novel dithiotosylate-mediated CC ring scission reactions $\text{1}$→$\text{2}$ and $\text{24}$→$\text{5}$ conveniently made available synthons towards a host of carbocyclic analogs of C-nucleosides. Unlike the past work, no chemoselectivity problems arose in generation of $\text{15}$.     

Remote inductive effects on secondary and tertiary 2-norbornyl solvolysis rates

A 5-cyano substituent decelerates the solvolysis rate of exo-2-norbornyl brosylate $\text{(1-H)}$ by a factor of 1790. A much smaller deceleration (24–90 fold) is observed for the secondary $\text{endo}$ and for both $\text{exo}$ and $\text{endo}$ tertiary 2-norbornyl derivatives. These results support the occurrence of σ-participation in the solvolysis of $\text{1-H}$.     

Per - bicyclophosphoranylation d'alditols

Reaction of bicyclophosphane $\text{1}$ with glycol $\text{2}$, glycerol $\text{3}$, erythritol $\text{4}$, L(-)arabitol $\text{5}$ and dulcitol $\text{6}$ leads to the corresponding per-alkoxybicyclophosphoranes $\text{2p}$ - $\text{6p}$ which are in tautomeric equilibrium with the phosphates forms $\text{2p}$′ - $\text{6p}$′.The amount of these latters increases regularly from traces to 24%.     

[O9,24] [2.1.2.1] metacyclophane-9-ene,a “twin cyclophane”, and its dehydrogenation products - synthesis structure determination and 1H-NMR-spectroscopy

The synthesis of [O⁹,24] [2.1.2.1]metacyclophane-9-ene and of its dehydrogenation products^the new pyrenocyclophanes $\text{8}$, $\text{10}$, $\text{11}$, and $\text{12}$, is described; their structures are discussed in connection with their ¹H-NMR-spectra.     

Synthesis,structure, and reactions of thiocarbonic acid derivatives new pentathiodipercarbonates, (RSS)2 CS, α,α,α-tris(disulfides), and the first α,α,α-tris(trisulfide)

Novel bis(perhaloalkyl) pentathiodipercarbonates $\text{5b-d}$ have been synthesized by reaction of sulfenyl chlorides with metal trithiocarbonates, and the heptathio analog $\text{21a}$ was prepared similarly. Lenthionine $\text{19}$ is the main product when diiodomethane is treated with sodium tetrathiopercarbonate. A rearrangement of bis(alkyldithio)chloromethanesulfenyl chlorides $\text{22}$ to alkyldithio) (alkyltrithio)dichloromethanes $\text{24}$ has been observed. Additions of sulfenyl chlorides and of thiosulfenyl chlorides to the thiocarbonyl compounds $\text{5}$ and $\text{21a}$ were achieved in acetonitrile. The structures of the first crystalline pentathiodipercarbonate $\text{5a}$ and α,α,α-tris(disulfide) $\text{29a}$, and of the first reported α,α,α-tris(trisulfide)$\text{31a}$ have been determined by X-ray crystallography.     

Induction asymetrique lors de l'addition de Michael d'un ester α-sulfinyle chiral

During the Michael addition of chiral α-sulfinyl eser (+) $\text{1}$$\text{R}$ on αβ-unsaturated esters, an extent of 24% of asymmetric induction was observed. It is shown that the addition products can be transformed into optically active δ-lactones.     

Thia-acyliminium - olefin cyclizations

Regioselective NaBH₄/H⁺-reduction of thiazolidinediones $\text{3}$-$\text{8}$ substituted at the nitrogen atom with different π-nucleophiles affords hydroxylactams $\text{9}$-$\text{14}$ in good yields. The latter compounds are excellent precursors for the α-acyliminium ion $\text{16}$ and can be stereoselectively cyclized in HCOOH to yield novel heterocyclic ring systems of varied structures. Because of the stereoelectronic control in the ring closure stereoselective syntheses, such as the conversion of $\text{8a}$ to $\text{24}$, are easily accomplished.     

Studies on the stereochemical course of intramolecular cycloaddition reactions of olefinic o-quinodimethanes-stereoselective synthesis of 8α, 9α, 14β-estranes

The stereoselective synthesis of 3-O-methyl-7α-$\text{p}$-toluenesulphonyl-8α, 9α, 14β-estradiol ($\text{25}$) and its 11-oxo derivative ($\text{26}$) $\text{via}$ thermolysis of 1β-$\text{tert}$-butoxy-2α-[2-(4-methoxybenzocyclobutenyl)ethyl]-2β-methy1-3α-[2-($\text{p}$-toluenesulphonyl)ethenyl] cyclopentane ($\text{22}$) and its oxo derivative ($\text{24}$), which were derived from condensation product ($\text{9}$) of optically active aldehyde ($\text{8}$) and 1-cyano-4-methoxybenzocyclobutene through $\text{10}$ and $\text{11}$ to selenides $\text{16}$ and $\text{21}$, is described.     

Synthesis of 26,26,26-trifluoro-25-hydroxy and 27-nor-26,26,26-trifluoro-25-hydroxyvitamin D3

Two new fluorinated 25-hydroxyvitamin D₃ analogs, 26,26,26-trifluoro- 25-hydroxy ($\text{1}$) and 27-nor-26,26,26-trifluoro-25-hydroxyvitamin D₃ ($\text{2}$), were prepared from 24-phenylsulfonyl 25,26,27-triorcholest-5-en-3β-yl tetrahydropyranyl ether ($\text{3}$).