Christopher P. Falshaw

Laurenyne, a new acetylene from Laurencia obtusa: crystal structure and absolute configuration

Abstract Laurenyne, a new chloroacetylene from the red form of the alga Laurencia obtusa has been identified and its crystal structure determined.

Revised structure of polyavolensin and its analogues

Abstract The structure of polyavolensin (4) has been determined by X-ray crystallography and the recently published structure needs revision.

Structure of antibiotic M139603; X-ray crystal structure of the 4-bromo-3,5-dinitrobenzoyl derivative

The molecular structure of antibiotic M 139603 has been determined from an X-ray crystallographic analysis of the 4-bromo-3,5-dinitrobenzoyl derivative.

Dehydration of dimeric 6-hydroxycyclohexa-2,4-dienones–an alternative course for these reactions and a model for the maytenone to anhydromaytenone transformation

Periodate oxidation of thymol gave the dimeric 6-hydroxycyclohexa-2,4-dienone (12), 3,10-dihydroxy-3,10-di-isopropyl-6,11-dimethyltricyclo[6.2.2.02,7]dodeca-5,11-diene-4,9-dione, and dehydration of this yields 4,11-di-isopropyl-7,12-dimethyl-13-oxapentacyclo[7.2.1.14,12.02,11]tridec-6-ene-5,10-dione (13). The structure of (13) rests upon its ozonolysis to yield anti-7-acetyl-4,9-di-isopropyl-1-methyl-5-oxo-10-oxatetracyclo[4.4.0.02,4.03,8]decane-9-carboxylic acid (15) which can be isomerised to give 1-hydroxy-2,7-di-isopropyl-5-methyl-10-oxo-6-oxapentacyclo[7.2.1.02,4.03,8.05,12]dodecane-7-carboxylic acid (21) with dilute aqueous sodium hydroxide. Alternatively acid catalysed isomerisation of (15) gives the syn isomer (19) and the X-ray crystal structure of the corresponding methyl ester syn-7-acetyl-4,9-di-isopropyl-1-methyl-5-oxo-10-oxatetracyclo[4.4.0.02,4.03,8]decane-9-carboxylic acid methyl ester (20) is reported. The dehydration of (12) to give (13) is considered to be a model for the transformation of the bis-diterpene maytenone into anhydromaytenone.

Compartmental ligands. Part 7. The reactions of 1,2-diaminobenzene and cis-1,2-diaminocyclohexane with heptane-2,4,6-trione and 1-(o-hydroxyphenyl)butane-1,3-dione. The crystal structures of 1-(o-aminophenyl)-2,6-dimethyl-4-pyridone hemihydrate and {3,3′-(cis-1,2-cyclohexanediyldi-imino)bis[1-(o-hydroxyphenyl)but-2-enonato]-(N,N′,O1,O1′)}copper(II)

The reaction of 1,2-diaminobenzene with heptane-2,4,6-trione yielded either the compound 2-(acetylmethyl)-4-methyl-3H-1,5-benzodiazepine or 1-(o-aminophenyl)-2,6-dimethyl-4-pyridone (5) depending upon the conditions used. The reaction of 1,2-diaminobenzene with 1-(o-hydroxyphenyl)butane-1,3-dione yielded a diazepine. In contrast the reaction of cis-1,2-diaminocyclohexane with heptane-2,4,6-trione yielded a tetramine macrocyclic compound, and with 1-(o-hydroxyphenyl)butane-1,3-dione afforded the compartmental Schiff base 3,3′-(cis-1,2-cyclohexanediyldi-imino)bis[1-(o-hydroxyphenyl)but-2-enone](10). The metal-complexing properties of this ligand are reported. Three-dimensional X-ray crystal-structure analyses have been carried out on compound (5) and on the mononuclear copper(II) derivative of (10), i.e. (12). Compound (5) has Z= 8 in a monoclinic cell with space group P21/c, and dimensions a= 14.984(1), b= 7.475(3), c= 21.173(1)A, and β= 98.71(1)°; R= 0.0388 for 2 392 reflections. Complex (12) has Z= 4 in a triclinic cell with space group P, and dimensions a= 13.143(8), b= 14.279(8), c= 14.289(14)A, α= 67.36(6), β= 71.18(7), and γ= 91.36(5)°; R= 0.0651 for 2 985 reflections. The structure shows the copper(II) to occupy the inner (N2O2) co-ordination site in an environment with a marked (ca. 14°) tetrahedral twist.

Ketene. Part 23. Conformational control of the addition reactions of ketenes with N-phenylnitrones

X-Ray analysis shows that the nitrone group in (5a) is not distorted, disproving a previous explanation for the formation of oxazolidinones rather than indolones in the reactions with ketenes. Nitrone (5c) reacts with dimethylketene and diphenylketene to form oxazolidinones (6c,d) whereas nitrones (5d) and (5e) under similar conditions form indolone derivatives (9). Oxazolidinone formation by the reaction of ketenes with nitrones (5a–c) results from restricted rotation about the N-phenyl bond preventing the [3,3]-migration (3)→(4), which precedes indolone formation.

Cycloadducts of nitrones with isocyanates; 1,2,4- or 1,3,4-oxadiazolidinones?

The adducts formed between various aryl-substituted nitrones and aryl isocyanates have been shown, using 15N n.m.r. spectroscopy and X-ray crystallography, to be substituted 1,2,4-oxadiazolidinones and not the previously reported 1,3,4-oxadiazolinones.

A novel spiro-biflavonoid from Larix gmelini

The unique spiro-biflavonoid structure of larixinol (1a) is described and a suggested pathway of biogenesis from dihydrokaempferol is proposed.

cis and trans Palladium(II) and platinum(II) complexes with 1,8-bis(diphenylphosphino)-3,6-dioxaoctane and their structural characterization. The first example of an eleven-membered diphosphine chelate involving cis geometry

Monomeric cis and trans complexes of PtII and PdII with 1,8-bis(diphenylphosphino)3,6-dioxaoctane (dpdo) of general formulae [M(dpdo)X2](M = Pd, X = Cl, Br, I, or NCS; M = Pt, X = Cl or I), in which the ligand binds only by the two phosphine donor atoms, have been synthesized and characterized by i.r., electronic, and 31P n.m.r, spectroscopy and molecular weight measurements. The isolation of these complexes illustrates that both cis and trans 11-membered chelate rings are obtainable under appropriate conditions; for example, both cis- and trans-monomeric [Pt(dpdo)Cl2] are reported. Syntheses of cis-palladium(II) complexes were carried out in polar solvents while trans isomers were prepared in less polar solvents. cis-Platinum complexes were prepared from [PtCl4]2– while the trans isomers were prepared from Zeises salt. Crystal structures of cis-[Pd(dpdo)Cl2] and trans-[Pd(dpdo)I2] are reported and discussed.

The X-ray crystal structure and absolute configuration of maytenol, a reduction product of the bis-diterpene maytenone

The X-ray crystal structure of the bis-diterpene derivative maytenol has been determined. The structure confirms the gross structure previously proposed for maytenone, and in addition the complete absolute configuration of these molecules is now firmly established. Thus maytenone (10) is the endo Diels–Alder dimer of (13αH)-13-hydroxyabieta-8(14),9(11)-dien-12-one (10).