Patents by Inventor Ravi Vankeepuram Jagannatha Chari

Ravi Vankeepuram Jagannatha Chari has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Process for the preparation and purification of thiol-containing maytansinoids
    Patent number: 6333410
    Abstract: The present invention provides a process for the preparation and purification of thiol-containing maytansinoids comprising the steps of: (1) reductive hydrolysis of a maytansinoid C-3 ester with a reducing agent selected from the group consisting lithium trimethoxyaluminum hydride (LiAl(OMe)3H), lithium triethoxyaluminum hydride (LiAl(OEt)3H), lithium tripropoxyaluminum hydride (LiAl(OPr)3H), sodium trimethoxyaluminum hydride (NaAl(OMe)3H), sodium triethoxyaluminum hydride (NaAl(OEt)3H) and sodium tripropoxyaluminum hydride (NaAl(OPr)3H) to yield a maytansinol; (2) purifying the maytansinol to remove side products when present; (3) esterifying the purified maytansinol with a carboxylic acid to yield a mixture of an L- and a D-aminoacyl ester of maytansinol; (4) separating the L-aminoacyl ester of maytansinol from the reaction mixture in (3); (5) reducing the L-aminoacyl ester of maytansinol to yield a thiol-containing maytansinoid; and (6) purifying the thiol-containing maytansinoid.
    Type: Grant
    Filed: August 18, 2000
    Date of Patent: December 25, 2001
    Assignee: Immunogen, Inc.
    Inventors: Ravi Vankeepuram Jagannatha Chari, Wayne Charles Widdison
  • Process for the preparation and purification of thiol-containing maytansinoids
    Patent number: RE39151
    Abstract: The present invention provides a process for the preparation and purification of thiol-containing maytansinoids comprising the steps of: (1) reductive hydrolysis of a maytansinoid C-3 ester with a reducing agent selected from the group consisting lithium trimethoxyaluminum hydride (LiAl (OMe)3H), lithium triethoxyaluminum hydride (LiAl(OEt)3H), lithium tripropoxyaluminum hydride (LiAl (OPr)3H), sodium trimethoxyaluminum hydride (NaAl (OMe)3H), sodium triethoxyaluminum hydride (NaAl(OEt)3H) and sodium tripropoxyaluminum hydride (NaAl(OPr)3H) to yield a maytansinol; (2) purifying the maytansinol to remove side products when present; (3) esterifying the purified maytansinol with a carboxylic acid to yield a mixture of an L- and a D-aminoacyl ester of maytansinol; (4) separating the L-aminoacyl ester of maytansinol from the reaction mixture in (3); (5) reducing the L-aminoacyl ester of maytansinol to yield a thiol-containing maytansinoid; and (5) purifying the thiol-containing maytansinoid.
    Type: Grant
    Filed: April 10, 2003
    Date of Patent: June 27, 2006
    Assignee: Immunogen, Inc.
    Inventors: Ravi Vankeepuram Jagannatha Chari, Wayne Charles Widdison