Recent Publications
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Synthesis of Porphobilinogen via a Novel Ozonide Cleavage Reaction J. Am. Chem. Soc. 2001, 123, 9307.
Porphobilinogen lactam Me ester (3a) has been prepd. in seven steps, and .apprx.20-30% overall yield, beginning with furfurylamine (4a).24 Hydrolysis of 3a following the literature procedure then gave porphobilinogen (1). A key intermediate in our synthesis of 3a is the 7-oxonorbornene deriv. 7a, which was derived from 4a utilizing a tandem Johnson ortho ester Claisen rearrangement followed by intramol. Diels-Alder cyclization (five steps, 55-65%).24 Interesting steric accelerating effects were obsd. in this sequence. Conversion of 7a to 3a was then accomplished employing a novel ozonide cleavage/oxidn. reaction, which generated tetrahydrofurans 16a, 32, and 33 in the proper oxidn. state for direct aminolysis to pyrrole 3a. A mechanism is proposed for the ozonide cleavage/oxidn. that accounts for the obsd. stereoselectivity of this step.
A New Synthesis of Chlorins Org. Lett. 2001, 6, 831.
A new synthesis of chlorins (I) (R1 = H, Me, Ph; R2 = H, Me; R3 = H, Me; R4 = Me, CH2CH2CO2Me) has been developed, based upon the acid-catalyzed condensation of dipyrrodialdehydes (II) with dipyrrylmethanes (III). A New Synthesis of Chlorins [Erratum for Volume 3, 2001]
Enantioselective Syntheses of 13C-Labeled (2R)- and (2S)-Phytochromobilin Dimethyl Ester Org. Lett. 2001, 6, 827.
(2R)- and (2S)-phytochromobilin di-Me esters (I) have been prepd. in enantiomerically pure form, specifically 13C-labeled at C10 or C15.
Enantioselective syntheses of (+)- and (-)-nephrosteranic acid employing the Nicholas-Schreiber reaction Can. J. Chem. 2001, 79, 1727.
(+)- And (-)-Nephrosteranic acid (I) have been prepd. in an enantioselective fashion from alkyne acid II (or ent-II) by a three step sequence involving debenzylation-lactonization, oxidative cleavage, and selective epimerization at C4. Acids II and ent-II were obtained as single enantiomers employing a Nicholas-Schreiber reaction.