An improved protocol for the construction of enantioenriched pyrrolidine, indoline, and piperidine rings using an organocatalyzed, intramolecular heteroatom Michael addition is described. Application to the enantioselective synthesis of homoproline, homopipecolic acid, and pelletierine has been accomplished.
An efficient enantioselective synthesis of cermizine D has been developed that exploits the use of a common intermediate to access over 85% of the carbon backbone. Key steps include an organocatalyzed heteroatom Michael addition, a diastereoselective alkylation with α-iodomethyl phenyl sulfide, a conjugate addition to a vinyl sulfone species and a sulfone coupling / desulfurization sequence to join the two major subunits.
The formal total syntheses of C5-epi-senepodine G and C5-epi-cermizine C have been accomplished through a novel diastereoselecetive, intramolecular amide Michael addition process. The total synthesis of cermizine D has been achieved through use of an organocatalyzed, heteroatom Michael addition to access a common intermediate. Additional key steps of this sequence include a matched, diastereoselective alkylation with an iodomethylphenyl sulfide and sulfone-aldehyde coupling/reductive desulfurization sequence to combine the major subunits. The utility of a Hartwig-style C-N coupling has been explored on functionally dense coupling partners. Diastereoselective conjugate additions to α,β-unsaturated sulfones has been investigated which provided the key sulfone intermediate in just six steps from commercially available starting materials. The formal syntheses of senepodine G and cermizine C have been accomplished through an intramolecular cyclization process of a N-Boc protected piperidine sulfone.
This paper describes JIGSAW. the massively parallel mask checking system that has evolved from our earlier feasibility study on large-scale, fine-grain parallelism in simple mask checking tasks [l]. Unlike previous systems, JIGSAW parallelizes all phases of the checking process. We describe new techniques to handle all-angle geometry, the first massively parallel mask flattening and multi-layer netlist extraction algorithms, and measurements made comparing JIGSAW, running on a Connection Machine, against industry-standard tools. End-to-end speedups, (i.e., from CIF to errors) range &om 19 to 58 over DRACULA, with larger masks producing larger speedups.
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