Cosme G. Francisco

Intramolecular hydrogen abstraction. Iodosobenzene diacetate, an efficient and convenient reagent for alkoxy radical generation

Photolysis of several hydroxy compounds in presence of iodosobenzene diacetate and iodine leads to alkoxy radical derivatives which undergo intramolecular hydrogen abstraction to produce cyclic ethers in good yield.

Synthesis of 1,4-epimine compounds. Iodosobenzene diacetate, an efficient reagent for neutral nitrogen radical generation

Abstract Photolysis of several nitroamines, cianamines, and phosphoroamidates in the presence of iodosobenzene diacetate (IBDA) and iodine leads to neutral aminyl radicals which undergo intramolecular hydrogen abstraction to produce epimine compounds with yields that are favorably compared with those obtained with the system lead tetraacetate and iodine.

Intramolecular hydrogen abstraction. Hypervalent organoiodine compounds, convenient reagents for alkoxyl radical generation

The photolyses of 5α-cholestane-3β,6β-diol 3-acetate (1), 5α-cholestan-2β-ol (4), 5α-cholestan-4β-ol (8), (20R)-pregn-5-ene-3β,20-diol 3-acetate (19), (20S)-pregn-5-ene-3β,20-diol 3-acetate (21), and dihydrotigogenin 3-acetate (25) in the presence of iodine and various hypervalent organoiodine compounds lead to alkoxyl radicals which undergo intramolecular hydrogen abstraction to produce, in most cases, 1,4-iodohydrins and tetrahydrofuran derivatives.

Steroidal N-nitroamines. Part 4. Intramolecular functionalization of N-nitroamine radicals: synthesis of 1,4-nitroimine compounds

Photolysis of 6β-nitroamino-5α-cholestane (4), 6β-nitroamino-5α-cholestan-3β-yl-acetate (5), 2β-nitroamino-5α-cholestane (13), 4β-nitroamino-5α-cholestane (17), (20R)-20-nitroaminopregn-5-en-3β-yl acetate (26), (20R)-(31) and (20S)-(34)-nitroamino-5α-pregnan-3β-yl acetate, (23R, 25S)-3β-acetoxy-23-nitroamino-5β-spirostan (46), 3β-nitroaminofriedelane (53), and methyl 3β-nitroaminofriedelan-29-oate (54) in the presence of iodine and various oxidative reagents leads to neutral nitroaminyl radicals which undergo intramolecular hydrogen-abstraction to produce in most cases N-nitroimine compounds. Best results were obtained with the system iodine and (diacetoxyiodo) benzene.

Long-acting contraceptive agents: testosterone esters of unsaturated acids

The synthesis of 13 new esters of testosterone is described, with the esterifying acids bearing acetylenic, olefinic, or polyunsaturated functions in the chain, for evaluation as long-acting androgens.

Intramolecular hydrogen abstraction. The use of organoselenium reagents for the generation of alkoxy radicals

Abstract The alkoxy radical intermediates, produced by photolysis of several hydroxy compounds in the presence of diphenylselenuranes (1) and iodine, undergo intramolecular hydrogen abstraction to afford cyclic ethers in good yield.

β-Fragmentation of alkoxy radicals. An approach to the synthesis of ring a of vernolepin

Abstract A model of ring A of vernolepin is synthesized by 1,4-fragmentation of γ-thiyl and γ-stannyl alkoxy-radicals, generated by photolysis of the corresponding δ-lactols ( 4 ) and ( 5 ) in the presence of iodosobenzene diacetate and iodine. It should be pointed out that the δ-lactone ring and the angular vinyl group are introduced in one step.

Intramolecular 1,8-hydrogen abstraction between glucopyranose units in a disaccharide model promoted by alkoxy radicals

3 pages, 3 schemes.-- PMID: 12491359 [PubMed].-- Supporting information available at: http://www.wiley-vch.de/contents/jc_2002/2002/z18262_s.pdf

Labdane diterpenes from Cistus symphytifolius

Abstract The investigation of the aerial part of Cistus symphytifolius afforded, in addition to sitosterol, trimethoxykaempferol, cativic acid, labdenic acid, labdanolic acid and labdan-8α,15-diol, three new bicyclic diterpenes: cistadienic acid, cistenolic acid and labd-13( E )- ene-8α,15-diol. The structures of these were determined by spectral studies and correlations. CD spectral studies showed that cistenolic acid and salvic acid are enantiomeric compounds, so the stereochemistry of salvic acid (7α-hydroxy-labd-8(17)-ene-15-oic acid) should be changed to 7β-hydroxy-eperu-8(17)-ene-15-oic acid (7β-hydroxy- ent -labd-8(17)-ene-15-oic acid).

Hypervalent organoiodine reagents in the transannular functionalisation of medium-sized lactams: synthesis of 1-azabicyclo compounds

The amidyl radical intermediates, produced by photolysis of medium-sized lactams 7-heptanelactam (1), 8-octanelactam (3), and 9-nonanelactam (6) in the presence of (diacetoxyiodo)benzene (DIB) and iodine, undergo transannular hydrogen abstraction to afford intermolecularly functionalised compounds such as oxoindolizidines (4) and (5) and the 1-azabicyclo[5.3.0]decan-2-one (7) that are obtained in high yield from lactams (3) and (6), respectively.