Tertiary Hydroxyl Research Articles

Protection of tertiary hydroxyl groups as methylthiomethyl ethers

Protection of tertiary hydroxyl groups as methylthiomethyl ethers

Transition metalcarbon bonds XXXVII. platinum acetylide complexes formed from ethynyl alcohols or ethers

Several new platinum(II) acetylide complexes, trans-{Pt[CCCR 1R 2(OR 3)] 2-L 2} (R 1, R 2  H, Me, Et; CR 1R 2  cyclohexylidene; R 3  H, Me or Ph), trans-[Pt(CCCH 2CH 2OH) 2L 2], trans-[Pt( p-tolylacetylide) 2L 2] and trans-[PtX( p-tolylacetylide)L 2] (L  PMe 2Ph or in one case, AsMe 2Ph) have been prepared. Platinum(II) acetylide complexes with tertiary hydroxyl groups are easily dehydrated by acetic anhydride/pyridine to give platinum-enyne complexes. Analogous compounds with primary hydroxyl groups do not dehydrate but give acetates. 1H and 13C NMR data are given and the shift reagent Eu(fod) 3 was used to analyse the 1H NMR spectrum of trans-[Pt(CCCH 2CH 2OH) 2(PMe 2Ph) 2].

The absolute configuration of phaseic and dihydrophaseic acids

A sample of phaseic acid methyl ester (5 mg, isolated from tomato plants fed (±)-abscisic acid, was reduced to a mixture of the epimeric dihydrophaseates which were separated by TLC. The more polar epimer was identical with the dihydrophaseate isolated from beans by Walton et al. [14]. Comparison of the NMR and IR spectra (H-bonding) of the two epimers shows the secondary hydroxyl of the less polar epimer is cis to the oxymethylene group, which is cis to the tertiary hydroxyl group. The absolute configuration of this centre is known so the absolute configuration of phaseic acid can be deduced. Phaseic acid is (−)-3-methyl-5{8[1( R), 5( R)-dimethyl-8( S)-hydroxy-3-oxo-6-oxabicyclo-(3,2,1)-octane]} 2- cis-4- trans-pentadienoic acid and both it and the reduction products exist in chair conformations. The more polar epimer isolated by Walton et al. is (−)-3-methyl-5{8[3( S,8( S)-dihydroxy-1( R,5( R)-dimethyl-6-oxabicyclo-(3,2,1)-octane]}2- cis-4- trans-pentadienoic acid. It is suggested that the less polar epimer should be referred to as epi-dihydrophaseic acid.

Reaction of primary-tertiary diacetylenic ?-glycols with hydrogen sulfide

The addition of hydrogen sulfide to primary-tertiary diacetylenic ζ-glycols in the presence of sodium ethylate is accompanied by dehydration involving the tertiary hydroxyl group and leads to the formation of 2 -(2′-hydroxyethyl)-5-alkenylthiophenes.

Carotenoid biosynthesis in Rhodopseudomonas spheroides. S-adenosylmethionine as the methylating agent in the biosynthesis of spheroidene and spheroidenone.

[methyl-(14)C]Methionine and S-adenosyl[methyl-(14)C]methionine were incorporated into the methoxycarotenoids spheroidene and spheroidenone by Rhodopseudomonas spheroides. The incorporation was greatly enhanced in the presence of lysozyme. On degradation of labelled spheroidene by hydriodic acid, the (14)C label was recovered in methyl iodide. Degradation of spheroidenone by reduction and allylic dehydration and demethylation of the reduction product gave a mixture of unlabelled carotenoid hydrocarbons, including 3,4-didehydrolycopene and 3,4-didehydro-7',8'-dihydrolycopene. The label from [methyl-(14)C]methionine and S-adenosyl[methyl-(14)C]methionine was located specifically in the methoxy group of spheroidene and spheroidenone. The biosynthesis of methoxycarotenoids in Rps. spheroides involves methylation of the tertiary hydroxyl groups of intermediates with S-adenosylmethionine.

Biosynthesis of spheroidene and hydroxyspheroidene in Rhodopseudomonas species: experiments with nicotine as inhibitor.

Neurosporene replaces spheroidene and hydroxyspheroidene as the main carotenoid in Rhodopseudomonas spheroides and Rhodopseudomonas gelatinosa grown in the presence of nicotine. On removal of the nicotine, spheroidene and hydroxyspheroidene are formed at the expense of the accumulated neurosporene. This shows that nicotine inhibits introduction of the C-1 tertiary hydroxyl groups, and supports the postulated pathway neurosporene-->spheroidene-->hydroxyspheroidene.

Synthesis of isobutylenediol dinitrate and some of its derivatives

1. Isobutylenediol dinitrate — the starting compound for the preparation of a number of isoerythritol derivatives — was synthesized. 2. In the case of the synthesis of diprimary isoerythritol dinitrate it was demonstrated that it is possible to prepare incomplete nitrates of polyatomic alcohols which contain vicinal primary and tertiary hydroxyl groups.

Approaches to the Synthesis of Gibberellic Acid. Construction of the B, C and D Ring System

Abstract One of the most challenging aspects of the synthesis of gibberellic acid2 and structurally related compounds such as steviol3 is the construction of the bicyclo[3.2.1]octane system with the unusual features of an exocyclic methylene group adjacent to a bridgehead tertiary hydroxyl group. In gibberellic acid this structural feature comprises the C, D ring system, which is fused to the five-membered B ring.

Die chemische struktur der biosynthetischen vorstufe des squalens

Presqualenyl-pyrophosphate (PSPP) was synthesized from farnesyl-pyrophosphate (FPP). The purified product could be transformed into a squalene in 90% yield. The structure of PSPP was established by the following experiments: 1.1) PSPP displays a remarkably acid-labile phosphate—ester bond. Analogous to FPP it was possible to stabilize this bond by the addition of bromine. This indicates a structure of the allylester type.2.2) On acid hydrolysis PSPP splits off not only the pyrophosphate but also water. This may be best explained by the presence of a tertiary hydroxyl group in PSPP.3.3) The pyrophosphate group of PSPP could be split by prostatic phosphatase. In gas-liquid-chromatography the trimethyl-silylated product gave a single peak. From the mass spectra of this compound and of the corresponding alcohol the expected molecular weight of 426 could be verified for the latter.4.4) Determining the 3H/14C ratio in 1-3H2-414C-FPP and in PSPP and squalene, synthesized from it, only three 3H-atoms could be detected in PSPP and in squalene.5.5) Ozonisation of PSPP, synthesized from 1-14C-FPP, gave radioactive malondialdehyde, which was characterised as azobenzene-malondialdehyde and 4-azobenzene-1-phenyl-pyrazole. The experimental results are in agreement with the following structure of 2, 6, 10, 15, 19, 23-hexamethyl-n-tetracosa-2, 6, 11, 14, 18, 22-hexaen-10-yl-pyrophosphate for PSPP.

Intramolecular facilitated acylation of a tertiary hydroxyl group in a perhydrobenzo[b]quinolizinetetrol

Intramolecular facilitated acylation of a tertiary hydroxyl group in a perhydrobenzo[b]quinolizinetetrol

Conversion of 5-(1,2-epoxy-2,6,6-trimethylcyclohexyl)-3-methylpenta-cis-2-trans-4-dienoic acid into abscisic acid in plants.

(+/-)-5-(1,2-Epoxy-2,6,6-trimethylcyclohexyl) -3-methyl[2-(14)C]penta-cis-2-trans-4-dienoic acid is converted into abscisic acid by tomato fruit in 1.8% yield (or 3.6% of one enantiomer if only one is utilized) and 15% of the abscisic acid is derived from the precursor. The 2-trans-isomer is not converted. The amounts of [2-(3)H]mevalonate incorporated into abscisic acid have shown that the 40-times higher concentration of (+)-abscisic acid in wilted wheat leaves in comparison with unwilted ones reported by Wright & Hiron (1969) arises by synthesis. The conversion of (+/-)-5-(1,2-epoxy-2,6,6-trimethylcyclohexyl) -3-methyl-[2-(14)C]penta-cis-2-trans-4-dienoic acid into abscisic acid by wheat leaves is also affected in the same way by wilting and it is concluded from this that the epoxide or a closely related compound derived from it is on the biosynthetic pathway leading to abscisic acid. The oxygen of the epoxy group was shown, by (18)O-labelling, to become the oxygen of the tertiary hydroxyl group of abscisic acid.

The chemical diversity of the plastochromanols

Two types of plastochromanols have been isolated and identified from leaf tissue. One type has a tertiary hydroxyl group in the isoprenoid side-chain and may be derived from plastoquinone C while the other has an esterified secondary hydroxyl function as found in plastoquinone B. These have been referred to as plastochromanol C and B respectively. In contrast to plastochromanol itself they are only found in photosynthetic tissue where they are present in only minor quantities compared with plastoquinone. These new plastochromanols are considered to be products of plastoquinone metabolism.

Studies on the constituents of Lyonia ovalifolia Drude var. elliptica Hand.-Mazz. XI. Structure of triterpenoid glucoside, lyofolic acid. 1

Lyofolic acid was reinvestigated by silica gel column chromatography and it was found to be contaminated with two minor components, one of which was identified as deacetyllyofolic acid. The molecular formula of lyofolic acid was revised as C38H62O11·2H2O. Alkaline hydrolysis of lyofolic acid gave a deacetylated compound, C36H60O10·3H2O, which was proved identical with one of the minor components. Hydrolysis of lyofolic acid with methanolic hydrogen chloride yielded lyofoligenic acid, C30H50O5, and glucose, and the signal of acetoxyl group disappeared in the nuclear magnetic resonance (NMR) spectrum of its aglycone. Genic acid contains one cyclopropane ring which has an isolated methylene group [chemical formula], two secondary and one tertiary alcohols, and one carboxylic acid group. Isopropylidene derivative was formed with acetone and p-toluenesulfonic acid between one secondary and one tertiary hydroxyl groups, [chemical formula].

Isomerization of 3,4-epoxyphospholanes

1. In the presence of catalysts of basic character, 3,4-epoxyphospholanes are isomerized to 2-phospholen-4-ols. 2. Unsymmetrical 3,4-epoxyphospholanes form a mixture of isomers, with a substantial predominance of the isomer containing a tertiary hydroxyl group.

Novel A-nor sterols: Synthesis and stereochemistry

A new and simple method of synthesis of A-nor sterols having a tertiary hydroxyl group allylic to an exocyclic methylene is described consisting of utilization of the Eschenmoser Fragmentation of αβ-epoxy ketones and the Stork Ring-closure of acetylenic ketones. 4 β,5 β-epoxycholestan-3-one gave 3-methylene-A-nor-cholestan-5 β-ol together with 3-methyl-A-nor-cholest-3-ene (III). The structure of the former was established by NMR, IR and by allylic isomerization. The stereochemistry at the 5 position was established by correlation with the diol and the minor epoxide obtained from III and to which configurations were assigned using NMR data. Exclusive formation of cis-hydrindane brings forth an unsuspected stereoselectivity in the Stork Ring-closure. The 17 β-hydroxyandrostane analogue was prepared via the pyranyl ether. With the hydroxyl unprotected the sole product in the Stork reduction was III (R = OH).

Studies on digitalis glycosides. 28. The structure of digiprogenin. (3).

From the results of lead tetraacetate oxidation of γ-digiprogenin 3-acetate as well as sodium metaperiodate oxidation of tetrahydro-γ-digiprogenin 3-acetate, the position of the tertiary hydroxyl group was revised to C-14 from C-17, and the new structure, 3β, 14-dihydroxy-14β, 17β-pregn-5-ene-11, 15, 20-trione (VIIIa) was assigned to γ-digiprogenin. α-Digiprogenin is its 17-epimer (IXa).

Hydrogen abstraction from methyl groups attached to an aromatic ring

The formation of cyclic ethers from methyl groups attached to an aromatic ring via decomposition of the hypobromite of a tertiary benzylic alcohol in an ortho position is described. The reaction occurs only for tertiary hydroxyl groups, and groups other than methyl are not functionalized.

Studies on digitalis glycosides. XXIX. The structure of digiprogenin. (4). Partial synthesis of dihydro-alpha-digiprogenin acetate.

14-Position of the tertiary hydroxyl group of γ-and α-digiprogenin (I and II) was established by partial synthesis of dihydro-α-digiprogenin 3-acetate (IIIb) from 11-oxo-tigogenin 3-acetate. Dehydration mechanism of α-digiprogenin (14-hydroxy-15, 20-dione type) to β-digiprogenin (16-ene-15, 20-dione type) was presented.

Zur Chemie des Phorbols, VIII

Oxidation of phorbol with one mole of lead tetraacetate yields bisdehydrophorbol, tiglophorbol and small amounts of phorbolacton-semiacetal. By chemical and spectroscopic investigations of bisdehydrophorbol and its derivatives its complete structure 16 is derived based upon the partial structures and structural elements of phorbol (1 - 3) which have been deduced in preceding communications. By consideration of the mechanism of the oxidative scission of the cyclopropanol unit in phorbol the structure 15 of this new tetracyclic diterpene is obtained. 15 has a pentamethyl-tetradecahydro-1H-cyclopropabenzazulene skeleton (tiglian) carrying as functional groups a tertiary hydroxyl group, an α,β-unsaturated tertiary 1.2-ketol group, a primary allyl alcohol group and a α- [hydroxycyclopropyl] -carbinol group. Phorbol is 4.9.12β.13.20-pentahydroxy-tigliadien- (1.6) -on- (3) (15) , bisdehydrophorbol 4.9.12β.20-tetrahydroxy-13.15-seco-tigliatrien- (1.6.15) -dion- (3.13) (16) the conformations of which have been determined. The structure of phorbolacton-semiacetal is determined in the following communication of this series. Based upon the structure of phorbol and additional chemical and spectroscopic evidence the structure of tiglophorbol (17) is also derived. With the data provided the relative configuration and the conformation of six out of the eight asymmetric centers of phorbol is determined.

Zur Chemie des Phorbols, V

In phorbol and partial acetates of phorbol the hydroxyl groups in the 20-, 13-, 12- and 4-positions can be etherified with one of the following methods: diazoalkane/Al-i-propylate, tritylchloride/pyridine and methyl-iodide/silveroxide. The investigation of suitable phorbol ethers with Fehling's and Tollens' reagent proves that the tertiary hydroxyl at the cyclopropane ring is solely responsible for the reducing properties of phorbol. Thus, phorbol is the first natural compound in which this reaction of tertiary cyclopropanols was detected.