Basilic Restaurant on Lido Island is absolutely fantastic. It's French with a slightly Swiss blend. Food is fantastic, they only serve French wine and they have only 25 seats or so. Intimate place but fabulous service. It's probably 30% cheaper than the Ritz at least with much better service, food and wine. They're house selection of wines is terrific. You could go big but wouldnt have to. Reservations a must because it is tiny. I rented the whole restaurant out two years ago for our Xmas party and they were fantastic.
Fashion Island area high rise has several nice choices:
Palm Terrace inside the Island Hotel
There's more to mention in that area, including some in Corona del Mar.
Newport Beach/Irvine High rise business district on east side (near freeways/airport) has a few nice choices:
6ix Park Grill (in Hyatt Regency Hotel, Irvine
)17900 Jamboree Rd., Irvine, CA, 92614
There's more in that area, but you gave us no parameters except "business" dinner.
Do you need table room? Lighting? Budget? Service habits?
The budget is fairly generous, but not too over the top (it's not an "expense account" in the bottomless-pit-of-money sense of the word)-and yes, business will actually be discussed over said dinner :)
If the dinner were being held in LA, some choices might be Luques, Spago or AOC, but probably not Cut or Providence, if that helps any. Table room is not an issue, nor is lighting, sound level can be moderate but being able to hear the person next to you speak is a must.
Sage on the Coast PCH in Crystal Cove Promenade or Sage Eastbluff in the residential area?
If at Crystal Cove Promenade on PCH (near Newport Coast), I would also recommend Modo Mio Cucina Rustica.
Modo Mio Restaurant Cucina
East Coast Hwy Newport Coast CA, East Coast Hwy Newport Coast, CA