RCAI-84, 91, and 105-108, ureido and thioureido analogs of KRN7000: their synthesis and bioactivity for mouse lymphocytes to produce Th1-biased cytokines

RCAI-84, 91, and 105-108 (1-6), the analogs of KRN7000 (A) with a ureido or a thioureido linkage instead of a carboxamido bond, were synthesized to examine their immunostimulatory activity against mouse lymphocytes. According to their bioassay, the ureido analog of KRN7000 RCAI-105 (1)] and its 6'-O-methylated derivative RCAI-106 (4)] induced a large amount of IFN-γ in mice in vivo. The hexadecyl ureido analog RCAI-84 (2)] was comparable to KRN7000 in its bioactivity. The octylureido RCAI-107 (3)], 5-phenylpentylureido RCAI-108 (5)], and thioureido RCAI-91 (6)] analogs were almost inactive.